In the wake of Friday's massacre at an Aurora, Colo., movie theater, law enforcement officials familiar with the investigation say the gunman must have had a substantial amount of target practice before the shootings. 
 
 They based their assessment on what they call the gunman's “unusually high” hit rate during the attack in the theater. Twelve people were killed, and 58 were injured. 
 
 The gunman used -- perhaps most notably -- an AR-15 assault-style rifle with a magazine that could hold as many as 100 rounds. But when that weapon jammed, authorities said, he switched to a less powerful weapon. He also carried a 12-gauge shotgun and a Glock .40-caliber pistol, authorities say. 
 
 Police said they recovered a second Glock from the suspect's car. 
 
 Among other things, the law enforcement officials said, authorities are searching the suspect's apartment for evidence of a gun range receipt, a brochure, related information he accessed on his computer or phone calls he may have placed to a range. 
 
 The officials are being briefed on the local investigation, but did not want to be named because of the sensitivity of the developing case. 
 
 Such evidence would go to the gunman's state of mind, the officials said, and provide more evidence of premeditation and that he deliberately planned the attack. For the government, investigators said, such evidence would tend to knock down any defense strategy that the suspect is insane. 
 
 Or the gunman could have simply gone out to the prairie east of Aurora and practiced alone, much like Tucson shooting suspect Jared Lee Loughner did before the attack in Arizona last year. 
 
 PHOTOS: 'Dark Knight Rises' shooting 
 
 One local shooting range owner said the suspect in the Aurora case, James E. Holmes, applied for membership at his club in June. But when the owner, Glenn Rotkovich, called Holmes, he was unnerved by the answering machine message. 
 
 "It was this very bass, guttural, rambling, incoherent message that was bizarre, at best," Rotkovich told the Los Angeles Times on Sunday. "Freakish, maybe." 
 
 Rotkovich ultimately told his staff not to follow through with Holmes without checking with him, but Holmes never showed up. The next time Rotkovich heard his name, it was on television. 
 
 Officials monitoring the local investigation in Colorado said the gunman displayed a high degree of marksmanship for an amateur. 
 
 They said he first fired the shotgun, which would have sprayed a large area of the theater with buckshot or pellets. Then he fired the semiautomatic AR-15 with the 100-round magazine. When that weapon jammed, he started shooting from the Glock pistol, they said. 
 
 Further, the gunman was shooting in a dark theater after midnight and aiming at moving targets, all amid a canopy of thick gas from canisters he'd set off. That environment, when combined with the kick from the shotgun and the Glock, would make firing with much precision all the harder. 
 
 To kill 12 people and wound 58 in that kind of chaos would be “unusually high for someone new to this,” one official said. 
 
 Officials also theorize that the suspect believed police were being drawn to an explosion at his apartment and that time was on his side. 
 
 When he burst out of the back of the theater, he probably had one of several plans in mind, they said. One, retrieve the second Glock from his white Hyundai and return to the theater, or drive off with the Glock and use it should he come under police fire, officials said. Or, as one official said, “turn the gun on himself.” 
 
 Instead, police were at the theater within two minutes and arrested the suspect before he reached his car. 
 
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 richard.serrano@latimes.com ||||| James Holmes seemed well on his way to a career as a scientist. 
 
 His résumé after he graduated with honors in neuroscience from the University of California-Riverside in 2010 cites experience in the lab dissecting birds, studying their musculature and analyzing data and graphs to measure molecules. 
 
 A video from a science camp he attended after high school shows him making a presentation about temporal illusions, misfirings in brain cells that lead to misreading the passage of time — the feeling that time stands still. In the video, Holmes refers to "an illusion that allows you to change the past." 
 
 He was one of six students admitted to the University of Colorado's graduate program in neuroscience last year. He received a $26,000 federal stipend. 
 
 But neuroscientist David Eagleman says Holmes' credentials were no better than those of an average student. The mass killing suspect is no elite neuroscientist, says Eagleman, of Baylor College of Medicine in Houston. 
 
 "He was just a second-year grad student," he says. "He didn't know anything." 
 
 Aurora, Colo., police say Holmes, 24, entered a midnight showing of the movie TheDark Knight Rises early Friday and opened fire with a rifle, shotgun and .40-caliber handgun, killing 12 people and injuring 58. They found his apartment booby-trapped with explosives and chemicals set to explode if someone entered. 
 
 Eagleman, a former researcher at the Salk Institute for Biological Studies in La Jolla, Calif., where Holmes attended the eight-week summer camp when he was 18, said the young man had a reputation as a "dolt." 
 
 Eagleman didn't know Holmes but says the teen parroted his advisers' words in his presentation on temporal illusions. A video of the speech was first reported by ABC News. 
 
 "He was just given the presentation to read," Eagleman says. "He wasn't any sort of superscientist when he was 18." 
 
 Stacie Spector, a Salk Institute spokeswoman, confirmed that Holmes attended a summer course at the institute but said that she could not comment further because of privacy concerns. She said the institute did not release the video. 
 
 John Jacobson, a former researcher at Salk whom Holmes listed as his mentor during the camp, told the Los Angeles Times that the teenager was a "mediocre" student who was stubborn and did not listen to direction. 
 
 "I saw a shy, pretty socially inept person," he told the newspaper. "I didn't see any behavior that would be indicative of violence then or in the future." 
 
 Jacobson told the newspaper Holmes "should not have gotten into the summer program. His grades were mediocre. I've heard him described as brilliant. This is extremely inaccurate." 
 
 He said Holmes' high school transcripts showed Bs and no advanced-placement classes. He was accepted to the camp because he had done computer programming, Jacobson said. He was never Holmes' mentor, he said, but Holmes worked in his lab to write a computer code for an experiment Jacobson was working on. He told the newspaper Holmes never finished it. 
 
 "What he gave me was a complete mess," Jacobson says. 
 
 Holmes' résumé suggests he was trained in dissection of birds and mice, performing chemistry tests and attaching small gene tags to cells to target them for treatment. 
 
 "Recipe-book stuff, literally, that every biology student should learn," Eagleman says. As for the grant, Eagleman says, "Holmes is being depicted as some sort of brilliant researcher who won a rare grant, but there are thousands of research students in this country with such grants. Everyone has one. There is nothing elite about it." 
 
 (Clarification: In our story published online Wednesday, Eagleman says he did not intend to suggest that all graduate students win research grants.) 
 
 Holmes had difficulty with a June 7 preliminary exam, given orally by three university faculty members. It is designed to evaluate students' knowledge at the end of the first year. Three days later, Holmes dropped out. ||||| University of Colorado officials disclosed Monday that mass shooting suspect James Holmes was being paid $26,000 a year for his studies, money that could have financed the cache of firearms, ammunition and explosive devices found in his apartment. 
 
 Holmes, 24, unexpectedly dropped out of an elite neuroscience graduate program June 10 after failing part of his first-year final exam. 
 
 School officials say they were stunned to learn of his arrest Friday after a shooting rampage at a packed movie house a few miles from campus that left 12 dead and 58 wounded. Police found Holmes' apartment near campus filled with booby-trapped explosive devices. 
 
 At an initial court appearance Monday morning, Holmes had orange hair and a dazed demeanor, a contrast to the doctoral candidate who arrived at the university with stellar academic credentials and references. He's due back in court July 30, when he is expected to face several first-degree murder charges. 
 
 "Everybody is in a state of shock," graduate school Dean Barry Shur said. "Everybody is upset. Who wouldn't be?" 
 
 The program to which Holmes was accepted last fall admits just six students a year. Candidates have top grades and "near perfect" test scores, Shur said. They undergo a background check but no mental examination. "No program requires psychiatric evaluation, to the best of my knowledge," 
 
 Holmes came with "excellent academic credentials," Shur said at a press briefing Monday flanked by school Chancellor Don Elliman and Executive Vice Chancellor Lilly Marks. 
 
 Shure and other administrators were at a loss to explain Holmes' motive, especially given Shur's comments that the faculty "tightly monitors" its neuroscience students. 
 
 Doctoral students receive free tuition, and most get federally sponsored 12-month grants of $26,000, about $500 a week. Holmes, who was not employed, bought an assault rifle, shotgun, two semi-automatic handguns and 6,000 rounds of ammunition in the months leading up to what police called a methodically planned shooting spree. 
 
 Officials say virtually no doctoral student has an outside job, given the intense nature of the program, which can take four or more years to complete. 
 
 Holmes has been described as a shy, quiet loner. Shur did not characterize him, but said scientists often immerse themselves in academics and research. "Scientists are quirky people," he said. "There are a lot of intense characters." 
 
 The preliminary exam, given orally by three professors, is designed to determine a student's basic knowledge and possible weaknesses, not weed anyone out, the officials said. The school would have provided remedial work and retesting if Holmes had sought help, Shur said. But after apparently failing June 7, he dropped out three days later. Campus Police Chief Doug Abraham said Holmes' school identification cards, which provide access to its facilities, were voided June 12. 
 
 School officials would not say if faculty contacted Holmes after his departure, but Shur said he never received forms from Holmes with an explanation for dropping out. "My understanding is he partially completed the forms but did not fill in his reason for leaving the program," Shur said. 
 
 School officials repeatedly deflected questions about Holmes' academic performance and details after he dropped out June 10, citing the ongoing criminal investigation into the case, but acknowledged it was unusual to quit. 
 
 Over the weeks before Holmes left, 90 packages containing ammunition and other items were shipped to the campus. Elliman said there was no way of knowing the volume or content of the shipments, which went directly to Holmes or to a campus mailroom. "We have thousands of packages that come here every day," he said. 
 
 The suburban Denver campus was on alert Monday, when a suspicious package was found at a professor's office and a second in a campus mailroom, school spokesman Daniel Meyers said. Both buildings were locked down but later reopened. 
 
 Authorities are checking whether materials from campus labs were used in the explosive devices found in Holmes' apartment.
– The latest in the attempt to better define Aurora shooter James Holmes: He apparently had a lot of target practice, isn't so smart, and may have a thing for prostitutes. From the most to least concrete: Based on Holmes' "unusually high" hit rate, police believe he had extensive target practice in advance of the shootings, reports the Los Angeles Times. To be able to kill or wound 70 moving targets in a dark theater cloaked in gas is no easy feat, and the kick from the shotgun (used to shower the theater with buckshot, or something like it) and Glock (which he switched to after his semiautomatic AR-15 jammed) only added to the difficulty level. Such a hit rate under those circumstances would be "unusually high for someone new to this," said one law enforcement official. So he was a skilled shooter—but was he brilliant? His neuroscience career path, his federal grant, that science camp video may indicate so, but the man Holmes listed as his camp mentor calls him a "mediocre" student; another neuroscientist says he was considered a "dolt," reports USA Today. He "should not have gotten into the summer program. I've heard him described as brilliant. This is extremely inaccurate." As for that $26,000 grant, "Everyone has one.There is nothing elite about it." (Business Insider speculates that the grant money could have paid for his weapons cache.) And then there's the latest from TMZ, which claims Holmes frequented prostitutes in the months before the attack. Click to hear from three women Holmes supposedly "reviewed" online.