NEWTOWN -- Investigators seized cellphones, computers and computer games during a search of mass murderer Adam Lanza's home -- but found no evidence that he was being treated with any drugs prescribed for mental illness, a source told Hearst Connecticut Newspapers.

Investigators are using search warrants to get medical records to determine if Lanza was being treated for a medical or psychiatric ailment, and what, if anything, was prescribed, the source said.

Lanza's parents told friends and divorce mediators that he had Asperger's syndrome, a form of high-functioning autism, but it is unclear if he had ever been formally diagnosed.

All this could be critical in determining what caused Lanza to crack and pump four bullets into his mother, Nancy Lanza, 52, who sources said was found dead in bed.

After killing his mother, Lanza grabbed two pistols, an assault rifle, a hunting rifle and hundreds of rounds of high-powered ammunition and went on a killing spree inside Sandy Hook Elementary School, mowing down 20 students and six staffers.

Hearing approaching police smash windows as they began entering the school, Lanza sought cover in another room and shot himself in the head, just about four minutes after his rampage began.

"It could have been a lot worse," said a second source, who was at the scene Friday. "He still had hundreds of more rounds. I'm convinced he would have continued going from classroom to classroom. He only killed himself because he heard the police arrive."

Detectives are poring through cellphone records and voicemails, viewing text messages and social network pages and analyzing computer equipment seized from his mother's upscale home, hoping to find answers.

"They are looking at everything," said Robert Paquette, who as an FBI agent investigated murders, organized crime and the Colombian drug cartel. "They are poring over anything and everything. Was he on meds? Did he go off meds? How was his relationship with his mother? What video games did he play? How often did he play? Where did he learn to shoot? How often did he shoot? ... Forensics are going to tell us who died where and when. What they want to determine is why."

Paquette said behavioral scientists, psychological and medical experts are likely on the team working with the State Police to uncover these answers.

"There's no one expert that will be able to tell all this," said Paquette, who also served as the FBI head in Bridgeport and the police chief in Danbury. "It's going to come from a conglomeration poring over the evidence."

But, he said, they may never come to a definitive conclusion.

"Unfortunately, the two people best able to tell are dead," he said.

Nancy Lanza's home on Yogananda Street and Sandy Hook Elementary School are being treated as guarded crime scenes for the foreseeable future, according to State Police Lt. J. Paul Vance, who would not comment on what was discovered during the search of the Lanza home.

"We did seize significant evidence at the residence," Vance said. "We do not discuss evidence, its content or detail what it is."

But much of the evidence seized involved video and Internet gaming material, according to a source.

"It's pretty clear he was an avid gamer," a source said.

"Many of these games are very, very violent," said Paquette. "I can't help but believe these can affect the minds of someone unbalanced."

Inside Sandy Hook Elementary School, dozens of rounds are still embedded in the walls, cabinets, closets and floors.

"I can't imagine what it looked like to go into that place," Paquette said. "No one could possibly be prepared to see something like that."

He wondered what Nancy Lanza, who reportedly took Adam to shooting ranges for target practice, was thinking by allowing her troubled son to learn to use an assault rifle.

"Maybe she was trying to be more of a friend to him than a mother," Paquette said.

The school is not expected to reopen this year and many question whether it should ever reopen.

On Monday, Gov. Dannel P. Malloy signed an emergency order allowing Newtown to transfer Sandy Hook's 500 kindergarten-through-fourth-grade students to Chalk Hill Middle School in Monroe for the remainder of the school year.

The governor also called upon churches across the state to ring their bells 26 times Friday at 9:30 a.m. in tribute to the victims.

Meanwhile, parents began the task of burying their children Monday.

Funerals for Noah Ponzer and Jack Pinto took place in Fairfield and Newtown, respectively.

Preparations by other families led to the release of more gruesome details of those horrifying four minutes that have broken a nation's hearts.

Ian and Nicole Hockley sought comfort by telling the world their 6-year-old special needs son, Dylan, died in the arms of his best friend, Anne Marie Murphy, a teacher's aide.

Staring down the barrel of Lanza's assault rifle, she pulled the boy close to her almost as if to shield him from the approaching hail of bullets.

"We take great comfort knowing that Dylan was not alone when he died," his parents, Ian and Nicole said in a prepared statement.

The Hockleys moved to Newtown from England just two years ago.