(CBS/AP) BOSTON - A former Navy SEAL from a Boston suburb was one of four Americans who died in the attack on the U.S. consulate in Libya Wednesday. 
 
 Forty-two-year-old Glen Doherty was killed with U.S. Ambassador Christopher Stevens in Benghazi, a family friend told CBS Boston on Thursday. 
 
 "He was on security detail and he was protecting the ambassador and also helping the wounded"' when he was killed, his sister, Katie Quigly told the Boston Globe. 
 
 Doherty was a 1988 graduate of Winchester High School. 
 
 A third victim has been identified as Foreign Service Officer Sean Smith, an Air Force veteran who had worked as an information management officer for 10 years in posts such as Brussels, Baghdad and Pretoria. 
 
 The identity of the fourth American killed is still not known. 
 
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 The four Americans were killed when a group of U.S. employees went to the consulate to try to evacuate staff as the building came under attack by a mob wielding guns and rocket propelled grenades. Stevens is the first U.S. ambassador to be killed in an attack since 1979, when Ambassador Adolph Dubs was killed in Afghanistan. 
 
 On Thursday, a senior Libyan security official said the attack was an organized two-part operation by heavily armed militants that included a precisely timed raid on a supposedly secret safe house just as Libyan and U.S. security forces were arriving to rescue evacuated consulate staff. 
 
 Wanis al-Sharef, eastern Libya's deputy interior minister, said Stevens and another American were killed in the consulate as plainclothes Libyan security were evacuating them to the safe house. The second assault targeted the safe house, killing two Americans and wounding nearly about 30 Libyans and Americans. 
 
 Meanwhile the Obama administration has begun what appears to be a terrorist hunt in Libya, as evidence mounts that the attack was perpetrated by well-armed thugs and not an out-of-control crowd. 
 
 CBS News correspondent David Martin reports the FBI has opened an investigation into the deaths, and agents will be sent to sift through the wreckage for evidence. They will be accompanied by a second team sent just for their protection. 
 
 As part of the hunt for the attackers, officials say the U.S. will increase its surveillance over Libya, including the use of unmanned drones. In addition, the U.S. Navy is positioning two destroyers armed with cruise missiles off the coast of Libya. 
 
 One destroyer, the USS Laboon, moved to a position off the coast Wednesday, and the USS McFaul is en route and should be stationed off the coast within days. Officials said the ships, which carry Tomahawk cruise missiles, do not have a specific mission. But they give commanders flexibility to respond to any mission ordered by the president. 
 
 The investigation will focus on whether the assault on the U.S. Consulate in Libya was a planned terrorist strike to mark the anniversary of the Sept. 11, 2001, attacks and not a spontaneous mob enraged over an anti-Islam YouTube video. 
 
 After the attack, an elite anti-terrorist unit of about 40 Marines was flown in to beef up security at the American embassy in the capital of Tripoli. Air Force transport planes flew the bodies of the dead Americans out, along with at least three who were injured and the rest of the approximately 25 diplomats assigned to the consulate. At the same time, the U.S. State Department urged all non-essential personnel to leave on commercial flights. 
 
 U.S. consulate attack in Libya 
 
 Three Americans injured in the assault on the consulate in Benghazi were being treated Thursday at the U.S. military hospital in Landstuhl, Germany, near America's Ramstein Air Base, CBS News has learned. 
 
 Wanis al-Sharef, a Libyan Interior Ministry official in Benghazi, said there had been threats that Islamic militants might try to take revenge for the death of al Qaeda's No. 2 commander Abu Yahya al-Libi, who was killed in a U.S. drone strike in Pakistan in June, and he said the U.S. consulate should have been better protected. 
 
 Confirming al-Libi's death for the first time in a video posted online Monday, al Qaeda chief Ayman Al-Zawahri called on Muslims in al-Libi's native Libya to take revenge for his death. 
 
 U.S. officials believe the militants were using the demonstration against the video as a cover to get into the consulate and then take as much revenge as they could on Americans, Martin reports. 
 
 While the White House has been hesitant to call the attack planned, House Intelligence Committee Chairman Mike Rogers was not so ambiguous. 
 
 "Absolutely it's a terrorist attack," Rogers told CBS News Capitol Hill producer Jill Jackson. "This was not done by the Libyan government. It was done by an external group we believe has at least extremist ties, maybe al Qaeda ties, and the style and the signature of the attack clearly would be something that we have seen before and would be in line with something al Qaeda would do." 
 
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 The White House says President Obama called the presidents of Libya and Egypt Tuesday and urged them to continue working with the United States to ensure the safety of diplomatic personnel. 
 
 Mr. Obama thanked Libyan President Mohamed Magariaf for his condolences over the deaths of Stevens and the three other State Department officers. The White House says the two leaders agreed to work together to bring the attackers to justice. 
 
 During a second call, Egyptian President Mohammed Morsi promised Egypt "would honor its obligation to ensure the safety of American personnel," the White House said. 
 
 Mr. Obama told Morsi that while "he rejects efforts to denigrate Islam ... there is never any justification for violence against innocents." 
 
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 next ||||| Enlarge Image Close Associated Press A Libyan man on Thursday investigates the inside of the burned-out U.S. consulate in Benghazi after an attack that killed four Americans, including Ambassador Chris Stevens. 
 
 BENGHAZI, Libya—The Libyan government arrested four people Thursday in connection with the deadly attack on the American consulate Tuesday night as Libyan and U.S. officials mounted a manhunt for others believed to be involved. 
 
 The Libyan government arrested four people Thursday in connection with the deadly attack on the American consulate Tuesday night as Libyan and U.S. officials mounted a manhunt for others believed to be involved. Matt Bradley reports. Photo: Reuters. 
 
 Hillary Clinton may have apologized for anti-Islam video but violent Middle East demonstrations against the U.S. continue to spread. WSJ's Matt Bradley reports from Cairo. Photo: AP 
 
 Protests spread across the region, breaking out in Yemen and Iran and once again in Cairo, where Egyptian police in riot gear beat back crowds of young men in a street filled with tear gas outside the U.S. Embassy. 
 
 Enlarge Image Close Mohamed al-Sayaghi/Reuters Protests continued in San'a, Yemen, where demonstrators scaled the U.S. Embassy fence. 
 
 In Yemen's capital, San'a, hundreds of young men breached the outer security rings of the fortified U.S. Embassy. Evidently inflamed by a video mocking the Prophet Muhammad, one young man in Yemen shouted, "Troops will not stand in our way in defending the honor of our Prophet.'' Still, there were indications some demonstrators were using the protests to put pressure on their countries' governments as much as to assail the video. 
 
 In the U.S., Secretary of State Hillary Clinton denounced both the anti-Islam video and the violence in Libya that took the life of U.S. Ambassador Christopher Stevens and three other Americans earlier this week. Emphasizing that the U.S. government had no role in the video, she called it "reprehensible" and said "we absolutely reject its content and message." At the same time, she said, there was "no justification—none at all—for responding to this video with violence." 
 
 As U.S. officials struggled to gain a clear picture of who was behind the mob attack in Benghazi late Tuesday, U.S. intelligence agencies were increasingly skeptical it was planned in advance, a shift from an initial assessment by some. U.S. officials also were increasingly doubtful the militants had direct ties to al Qaeda. 
 
 The information pointing to the possibility of a more spontaneous assault could deflect criticism of both the U.S. and Libyan governments for missing clues to an impending attack. An impromptu attack without clear ties to a major terrorist organization also could ease pressure on U.S. officials to respond aggressively. 
 
 The third and fourth Americans killed in the attack on the U.S. consulate were identified by the State Department late Thursday as security personnel Tyrone S. Woods and Glen A. Doherty, both former Navy SEALs. Previously identified, in addition to Mr. Stevens, was State Department information officer Sean Smith. 
 
 Romney campaign adviser Kevin Madden discusses the GOP nominee's response to the attacks in the Middle East. WSJ reporters analyze what it means for the campaign and look ahead to the risks posed by the nation's fiscal woes. 
 
 The events continued to reverberate in the U.S. presidential campaign, in a more muted form than on Wednesday. Republican Mitt Romney didn't repeat his criticism that the Obama administration was "effectively apologizing for the right of free speech" but said in Fairfax, Va., that the Libyan attack showed that "a strong America is essential to shape events." 
 
 In the wake of the deaths of four American diplomats in the Middle East, WSJ reporters assess the the impact foreign policy might have on the campaign. Moody's threatens the U.S. with a downgrade and Bill Clinton continues to stump for Obama. 
 
 President Barack Obama, campaigning in Colorado, promised that "no act of terror will go unpunished.'' Mr. Obama also has led a U.S. effort to moderate the reaction to the film in Muslim countries and stem protests in advance of Friday prayers, which often lead to new demonstrations in Muslim lands. 
 
 Timeline: Past Attacks Past attacks on U.S. embassies and consulates around the world. View Graphics Turmoil Spreads Photos View Slideshow Reuters A protester shouted slogans during clashes with riot police along a road leading to the U.S. Embassy in Cairo Friday. 
 
 A Libyan official in charge of a task force tracking a militant group whose members led the first wave of attacks said his country was throwing all available resources into the hunt. Wanis al-Sharif, a deputy interior minister, said his team was using telephone taps, among other tools, to follow the group, hoping for a better understanding of its strength and structure. 
 
 "There is a group now that is under our custody, but there is a group we're following to know who's connected to them, and [we] are monitoring their phone calls," Mr. Sharif said, declining to provide more details. 
 
 The U.S. role in the manhunt has remained low key, in part out of concerns that a heavy overt American role would inflame tensions. But the U.S. has ramped up intelligence collection in the region, using unmanned aerial drones and other sophisticated eavesdropping equipment, officials said. 
 
 The distinctive humming motors of drones could be heard in the skies above Benghazi Thursday. The U.S. has used drones and other intelligence-collection efforts since the fall of Col. Moammar Gadhafi to track militant camps and weapons caches in areas east of Benghazi known to be Islamist hotbeds. 
 
 The focus of the Libyan probe appears up to this point has been an Islamist rebel brigade called Ansar al Sharia, a group of fundamentalist religious men who banded together in a militia last year in the fight to oust Gadhafi. Members of the group were at the consulate attack and cars belonging to members were found abandoned in the area, according to Mr. Sharif. It isn't known whether the four men arrested are members of the group. 
 
 A spokesman for Ansar al Sharia, Hani Mansouri, said at a news conference Thursday that his organization didn't organize or participate in the attack. 
 
 U.S. officials said preliminary information suggests the militants saw protests sparked by an anti-Islamic video as an opportunity to wreak havoc on a prominent symbol of the U.S. to make an anti-American statement. "There is no intelligence indicating this was premeditated," a U.S. official said. "It looks like it was an opportunistic attack by a group in the region." 
 
 There also are no indications at this point that the attackers knew the ambassador was in the building. 
 
 Around Benghazi, Libyan forces made no discernible ramp-up of security. A unit of six lightly armed Libyan defense soldiers stood outside the burned-out consulate complex Thursday afternoon. 
 
 The siege began late Tuesday night. New descriptions by Libyan security officials detailed hours of terror in which outgunned consulate security forces tried in vain to battle well-armed assailants. 
 
 Enlarge Image Close Kevin Hagen for the Wall Street Dilan Samo, right, and Jeje Barwary hold photos during a candlelight vigil in honor and memory of slain American Ambassador to Libya Christopher Stevens outside the permanent mission to Libya in Manhattan on Thursday. 
 
 Mohammed Farraj, a soldier who was part of a four-member Libyan military unit permanently stationed at the facility. said he heard commotion on the dirt road outside the compound about 8:30 p.m. and was told by walkie-talkie of a group of armed, bearded protesters gathering. 
 
 There also were four private security guards, all Libyans, who weren't armed and worked inside the compound. Interviews with the Libyans indicated there also were four to eight American security guards around the compound when the attack started. 
 
 As trouble began, two Libyans posted on the outside moved inside and alerted the Libyan security forces, said Mr. Farraj, but backup didn't arrive immediately. Mr. Sharif said that he advised the armed security unit not to open fire so as to not inflame the situation. 
 
 Stream: Libya Attack Follow real-time coverage of the attack in Libya against the U.S. embassy and the unfolding unrest. 
 
 Fighting erupted at about 9:30 p.m., said Abdulaziz Mezhbury, who works for a Libyan-British security firm called Blue Mountain and was responsible for security around the main villa. Mr. Mezhbury faced a storm of grenades and small-arms fire from militants who had breached the 12-foot wall around the compound. He was shot three times in the leg and suffered shrapnel wounds from grenades. 
 
 As the compound was being overrun, the Americans started returning fire, said Mr. Farraj. "But we were totally outgunned. I called more of the brigade to come reinforce us." He said a lull developed around 11 p.m. and the Americans and Libyan military appeared to be back in control. At this point, Mr. Farraj said, he believed that the bulk of the American consulate staff were evacuated. But the ambassador was missing and the villa was on fire. 
 
 The security guards made a decision to brave the flames to find the missing ambassador but were beaten back by the fire and couldn't find Mr. Stevens. 
 
 —Julian E. Barnes, Siobhan Gorman and Hakim Almasmari contributed to this article. 
 
 Write to Margaret Coker at margaret.coker@wsj.com
– Four people have been arrested for their connection to the protests at the US consulate in Libya that left four Americans dead, including Ambassador Chris Stevens, information management officer Sean Smith, and a former Navy SEAL. There may be more arrests in the near future, as security forces in the country say they have a large group of people in custody and are monitoring others who may be connected to the protests, reports the Wall Street Journal. Meanwhile, the name of the third victim has come to light. Family of 42-year-old Glen Doherty, the former SEAL who hailed from a Boston suburb, has confirmed that he was killed in the attacks, reports CBS News. The identity of the fourth American victim remains unknown.