"By NBC News staff and wire services Updated at 8 p.m. ET: A picture of Adam Lanza slowly emerged Saturday, as acquaintances said his behavior included pressing up against walls to avoid others and clutching his briefcase. Investigators, meanwhile, said they hoped that "very good evidence" found at his home would shed light on what pushed him to kill 26 children and teachers as well as his mother. Connecticut State Police Lt. Paul Vance said Saturday that investigators had found "very good evidence ... that our investigators will be able to use in painting the complete picture, the 'how' and, more importantly, the 'why this occurred.'" But he would not elaborate and the mystery deepened as education officials in Newtown, Conn., said they had found no link between Lanza's mother and the school, contrary to news reports that said she was a teacher there. Connecticut school shooter was 'very nervous around people' - U.S. News -------------------------------------------------------------------------------- Investigators said they believe Lanza, 20, attended Sandy Hook Elementary many years ago, but they had no explanation for why he went there on Friday. Lanza shot and killed his mother, Nancy Lanza, at the home they shared, then drove to the school in her car, forced his way inside and opened fire in two classrooms, authorities said. Within minutes, he killed 20 children, six adults and himself. Authorities said Lanza had no criminal history; it was not clear whether he had a job. His father, who learned about the shooting from a reporter at the Stamford Advocate, said in a statement that he was in a "state of disbelief and trying to find whatever answers we can." Lanza said he has cooperated with law enforcement and will continue to do so. Meanwhile, acquaintances described the former honor student as smart but odd and remote. "We would hang out, and he was a good kid," Joshua Milas told The Associated Press. He said he had not seen Lanza in a few years. "He was probably one of the smartest kids I know. He was probably a genius." "(His mother) pushed him really hard to be smarter and work harder in school," Tim Arnone told Reuters. He first met Lanza at Sandy Hook Elementary School. "He was very different and very shy and didn't make an effort to interact with anybody" in his 10th-grade English class at Newtown High School, Olivia DeVivo told the AP. DeVivo, now a student at the University of Connecticut, said Lanza always came to school toting a briefcase and wearing his shirt buttoned all the way up. "Now looking back, it's kind of like 'OK, he had all these signs,' but you can't say every shy person would do something like this," she said. Richard Novia who until 2008 was the school district's head of security and adviser to the school's technology club, of which Lanza was a member described Lanza to the AP as "a loner." "You had yourself a very scared young boy, who was very nervous around people," he added. Novia said Lanza had extreme difficulties relating to fellow students and teachers, as well as a strange bodily condition: "If that boy would've burned himself, he would not have known it or felt it physically." Lanza would also go through crises that would require his mother to come to school to deal with them. Such episodes might involve "total withdrawal from whatever he was supposed to be doing, be it a class, be it sitting and reading a book," Novia told the AP. When people approached Lanza in the hallways, he would press himself against the wall or walk in a different direction, clutching his black briefcase "like an 8-year-old who refuses to give up his teddy bear," said Novia, who now lives in Tennessee. Even so, Novia said his primary concern about Lanza was that he might become a target for teasing or abuse by his fellow students, not that he might become a threat himself." This is the same old story as in Columbine... just delayed by 12-15 years. The kid was picked on.