NEWTOWN, Conn. -- As many as a half-dozen first-graders may have survived Adam Lanza's shooting rampage at Sandy Hook Elementary School because he stopped firing briefly, perhaps either to reload his rifle or because it jammed, according to law enforcement officials familiar with the events.
A source said the Bushmaster rifle that Lanza used in the shooting is at the state police forensic laboratory undergoing several tests, including tests to determine whether it was jammed.
The children escaped from the first-grade classroom of teacher Victoria Soto, one of the six adults Lanza killed in the school after shooting his way through a glass door with the .223-caliber semi-automatic rifle on the morning of Dec. 14.
On Friday, detectives obtained and began examining records related to psychiatric care Lanza had received in an attempt to determine a motive. Several friends of his mother have said that he had Asperger's syndrome, but authorities have not confirmed that or indicated that it had anything to do with the shootings.
Lanza killed 27 people -- 20 children, four teachers, the school principal, a school psychologist and his mother, Nancy -- before fatally shooting himself in the head as police began arriving at the school.
The arriving officers encountered a shocking scene in Ms. Soto's classroom. Lanza had shot her, as well as special education teacher Anne Marie Murphy and six of Ms. Soto's 6- and 7-year old students. Seven other children were found unharmed in a classroom closet, apparently hidden by Ms. Soto when she heard shooting. The other students fled the classroom.
Based on initial statements from surviving children and the fact that unfired bullets from Lanza's rifle were found on the ground, detectives suspect that some students were able to run to safety when Lanza stopped firing, probably for a short period of time, the officials said.
It is possible that Lanza mishandled or dropped a magazine and unfired bullets fell to the floor as he reloaded the rifle frequently, they said.
But it also is possible, they said, that the mechanism that fed bullets into the rifle jammed, causing Lanza to remove the magazine and clear the weapon. Unfired bullets could have fallen to the classroom floor during that process as well, law enforcement officials said.
The six children who escaped Lanza's rampage ran to a private home a short distance from the school.
The authorities have learned generally from the children who ran away that something may have happened to Lanza's rifle that caused him to stop firing. The substance of the statements, which are not entirely consistent, is that a piece of the weapon, probably a magazine holding live bullets, was dropped or fell to the classroom floor.
Given the chaotic nature of the scene, it is also possible that some children escaped while Lanza was shooting others in the room.
State police are expected to wrap up work at the school and release it as a crime scene in the next few days. They still are trying to determine how many shots Lanza fired.
Lanza killed himself in Ms. Soto's classroom with one of the two pistols he carried into the building. Police found a loaded 20-round shotgun in the trunk of the car similar to what is known as a "street sweeper." Police believe that Lanza didn't bring it into the school because he couldn't carry all of the weapons and ammunition. Lanza, who was about 6 feet tall, weighed barely 110 pounds, law enforcement sources said.
The few people who knew Lanza have portrayed him in the days since the mass shootings as an awkward, emotionally isolated, withdrawn young man. He attended public schools in Newtown, but at times was home-schooled by his divorced mother, who was said by authorities and others to be the only person with whom he was socially engaged.
Lanza lived with his mother. He had two bedrooms and used one of them to keep computer equipment on which he is said to have enjoyed playing video games involving violent war games.
Sometime before the shootings at the elementary school, Lanza shot his mother four times with a .22-caliber rifle as she lay in bed. He left the rifle at the house. All the guns were registered to Nancy Lanza.
Adam Lanza also broke apart his computer equipment in a way that has prevented authorities from retrieving data.
He then drove to the school, getting there around 9:30 a.m. He walked up the front entrance and fired at least a half-dozen rounds into the glass doors. The thunderous sound of Lanza blowing an opening big enough to walk through in a locked school door, caused principal Dawn Hochsprung and school psychologist Mary Scherlach to bolt from a nearby meeting room to investigate.
He shot and killed them both as they ran toward him. Two other staff workers in a meeting with Ms. Hocksprung and Ms. Scherlach were injured in the hail of bullets but made it back inside the conference room where one called 911 from under a table.
Lanza then turned toward the first classroom on his left, that of teacher Kaitlin Roig. By then, authorities said Ms. Roig had hidden with her students in a closet in her classroom. Before securing the closet door, which opened inward, authorities said, she concealed the door behind a moveable bookcase.
Lanza then walked past Ms. Soto's classroom into the third one, where substitute teacher Lauren Rousseau was teaching. He shot and killed Ms. Rousseau, a special education teacher, and 14 students.
One member of the class was not killed, although it is unclear if the child escaped the shooting or was not in the room.
"I think the community is very much respecting their privacy. I think that everyone is very sensitive to what a horrific experience this 6-year-old has been through," Newtown's superintendent of schools, Janet Robinson, said.