Connecticut school shooting: Adam Lanza rigged rifle for maximum damage Wayne Carver, the Connecticut medical examiner, said Lanza used a technique known to gun enthusiasts as "jungle-taping." This helps explain how the killer was able to wreak so much carnage in a shooting spree that may have lasted barely five minutes. Dannel Malloy the Connecticut governor, disclosed that Lanza broke into the school by firing a volley of bullets through a secured door and killed himself when he when he heard police arriving while he was still gunning down children. That raised the prospect that the death toll might have been even higher if the emergency services had not reached the site so quickly. Police found seven terrified children cowering in the cupboard of a second room after Lanza wiped out one class of six and seven-year-olds and their two teachers. There were 14 coats hanging there and 14 bodies. He killed them all," a law enforcement officer told the Hartford Courant. The bullets used in the massacre were designed specifically to penetrate deep tissue and do a "devastating" amount of damage. Weapons experts believe the killer used "frangible ammunition," which fragments on impact, inflicting wounds that are usually beyond medical help. The weapons were all owned by Mrs Lanza, who was reportedly in bed when her son killed her with shots to the head before driving to the school. Lanza is believed to have fired at least three 30-bullet magazines with chilling accuracy - only two people, both teachers, survived their injuries. FBI electronics experts are poring over the broken hard drive trying to determine what is likely to be crucial evidence about how he planned his killing spree, with whom he exchanged messages and what websites he visited. Lanza had been a member of a school computer "geek" club in his teens. The 4chan website used by hackers and cyber extremists was said to have featured a warning last Wednesday from an anonymous user that he planned a school rampage in Connecticut on Friday morning, but there have been claims that the posting was a hoax. Federal agents are also visiting gun stores and shooting ranges amid reports that Mrs Lanza taught her son to shoot. They are also questioning relations, including Mrs Lanza's ex-husband and her older son, both of whom were estranged from the gunman. Investigators are not believed to have found a suicide note or manifesto of the sort left by the killer of 32 fellow students and staff at Virginia Tech in 2007. Why Lanza selected the school for his rampage is not known. His mother was initially reported to have been a teacher there, but education officials later denied such a link existed. It is believed Lanza attended Sandy Hook before going on to other schools in the town. A relation said Mrs Lanza pulled her son out of school in his mid-teens and taught him at home as she was unhappy with education board plans for him. The report that he obsessively played violent criminal games will raise fresh questions about the impact of such games on disturbed individuals. Based on interviews with law enforcement officials, the Hartford Courant provided the clearest description yet of what investigators believe that Lanza did after he shooting his way into the school. His first victims were the headmistress Dawn Hochsprung and school psychologist Mary Scherlach who came running into the corridor after hearing the burst of gunfire in the entrance. Lanza shot them both dead as Mrs Hochsprung reportedly attempted to tackle him. He then passed the first classroom he reached, where Kaitlin Roig had barricaded her children inside a bathroom. He moved to a classroom where he systematically shot all those inside - 14 children whom the Courant reported were huddled and clutching each other in terror - and two teaching staff. Lanza then reached the classroom of Victoria Soto, who is believed to have hidden some of her students in a classroom cupboard. Miss Soto tried to divert him by saying that her children were in another room, but he shot her and a teacher's aide and several pupils who tried to escape. Additional reporting by Tom Teodorczuk in Newtown