suspected Sunni rebels, dressed as Iraqi police commandos, stormed the Al Askari Mosque in Samarra—a mosque particularly holy to the Shi'a majority and the location where several imams are buried. Although there were no casualties in the attack, the bombing leveled the mosque and caused unprecedented anger amongst the Shi'a majority, prompting death squads, largely from the Mahdi Army, to roam the streets of Baghdad and other major cities, attacking Sunni mosques, killing Sunni civilians and murdering Sunni clerics. The Sunni insurgents and populace soon organized into their own defensive units and death squads and began further revenge killings, causing a spiral of violence that took the country into a full blown civil war. Violence throughout the spring was largely dominated by inter-Iraqi fighting, leaving the U.S.-led coalition forces unsure of their next move as death squads engaged in tit-for-tat revenge killings. U.S. commanders were forced to admit that this level of violence was unprecedented in the three years of American occupation and reconstruction, although both political and military leaders in the United States and Iraq continued to insist that the country was not on the verge of civil war. The Interior Ministry, the ministry responsible for internal policing and headed by a Shi'a party (the Islamic Supreme Council of Iraq), was suspected of utilizing entire police squads for sectarian killings and torture. Sunni communities grew fearful of approaching Iraqi police commandos, and some that had stayed out of the insurgency and the revenge killings formed militias to defend themselves against what they viewed as Shi'a aggression and encroachment. Often, these militias would open fire on police or army units that were not accompanied by American or otherwise coalition soldiers. Suicide attacks dropped during the period in exchange for largely underreported single killings, and also included a few spectacular, brazen daylight raids on Sunni or Shi'a communities by masked gunmen who executed large numbers of opposing sect members. Bomb attacks on Sadr City, the stronghold of the Mahdi Army, resulted in the Mahdi Army moving onto the streets to exact revenge on largely uninvolved Sunni civilians. Neither the U.S. Army, nor the Iraqi Defense Ministry, were making headway in stopping the attacks. By June 2006, the UN reported that 100 civilians a day were dying in Baghdad alone due to sectarian violence. On June 7, 2006, U.S. warplanes bombed a house north of Baghdad where terror leader Abu Musab al-Zarqawi