(NEW YORK) -- Adam Lanza, the 20-year-old who killed 20 children and six adults in a rampage at a Connecticut elementary school, and his mother both spent time at an area gun range, ABC News has learned.
A Bureau of Alcohol, Tobacco, Firearms and Explosives spokesperson told ABC News investigators have determined Lanza did visit a gun range, but they have not determined whether he shot there.
Investigators have also learned his mother, Nancy Lanza, visited a gun range on multiple occasions, but they have not determined whether her son was with her during those visits, the spokesperson said.
ATF agents have been canvassing area gun ranges and gun dealers to learn whether Adam Lanza had been a customer or a visitor.
Law enforcement sources tell ABC News that reports that the shooter recently attempted to purchase a gun at a local sporting goods store have not been substantiated at this time.
Adam Lanza used a Bushmaster .223 semi-automatic rifle at close range to kill children and adults at Sandy Hook Elementary School in Newtown, Conn., on Friday.
Two handguns were also found at the scene, but law enforcement officials described the Bushmaster as the primary weapon. A fourth weapon was found nearby. The weapons discovered at the school apparently belonged to a family member, possibly his mother, according to authorities.
Adam forced his way into Sandy Hook on Friday morning and killed 20 children and six adults before committing suicide. He drove to the school after shooting his mother in the face at their home.
The weapons that police recovered from the scene included a Glock 9-mm handgun, a Sig Sauer 9-mm handgun and a Bushmaster rifle. Police also found .223 shell casings. Adam was wearing a bulletproof vest.
The shooter's mother, Nancy, 52, had five weapons registered to her, including a Glock, a Sig Sauer and a Bushmaster rifle.
Police said the Glock, the Sig Sauer and the Bushmaster at the school appeared to be registered to a family member. Authorities are currently completing their checks to see which weapons were used in the slayings, to whom they were registered and how they were obtained.
Adam, who was described by neighbors and former classmates as being very bright, took six classes at Western Connecticut State University in 2008 and 2009, beginning when he was just 16, and had a grade-point average of 3.26.
According to Paul Steinmetz, director of University of Relations at Western Connecticut State University in Danbury, Adam started at the school in the summer of 2008, took a couple of classes that fall and then in the spring and summer of 2009.
A 16-year-old attending classes is rare, but not unique, Steinmetz said. He said that some high school students sign up for classes at the college if they are particularly good in some subject. He said the school has probably a few 16-year-olds every semester.
Adam took courses in computer science, such as website design, the computer language called BASIC, and data modeling, as well as in philosophy, American history and economics.
Steinmetz said he had not heard from anybody on the staff who has any knowledge of Adam at all, but it would be unusual for a professor to remember a student in a class from four years ago. He said that in the classes Adam took there would likely be 20 to 25 students.
Long before Adam's spree, residents of Newtown had noticed that the tall, pale boy was different, and believed he had some kind of unspecified personality disorder.
"Adam Lanza has been a weird kid since we were five years old," wrote a neighbor and former classmate Timothy Dalton on Twitter. "As horrible as this was, I can't say I am surprised."
In school, Adam carried a black briefcase and spoke little. Every day, he wore a sort of uniform: khakis and a shirt buttoned up to the neck, with pens lined up in his shirt pocket.
A former classmate in his 10th-grade honors English class, Olivia DeVivo, says he "was always very nervous and socially awkward."
She told ABC News that "he didn't really want to be spoken to" and that when teachers would call on him "it appeared physically difficult for him to speak."
Adam avoided public attention and had few, if any, friends, though he was a member of the high school tech club. He liked to sit near the door of the classroom to make a quick exit.
Copyright 2012 ABC News Radio