The man suspected of gunning down more than two dozen people in a small town in Connecticut is the son of a teacher at the elementary school where the killings occurred, and his mother is presumed to be among the dead.
A law enforcement official says that the shooter brought three guns into the school. The weapons were all registered to his slain mother.
Police say Adam Lanza apparently drove to his mother's school carrying two handguns and a .223-caliber rifle and carried out the massacre. Law enforcement officials are trying to learn as much as possible about the 20-year-old and questioning his older brother, who is not believed to have any involvement in the rampage.
The official cautions that investigators haven't conclusively linked the guns used in the rampage to the ones the woman owned.
The official says state police records show the woman had legally purchased five firearms and all were registered in Connecticut. Authorities are still trying to account for all the guns.
So far, authorities have not spoken publicly of any possible motive.
Several neighbors of the Lanzas in Sandy Hook, a community about 60 miles northeast of New York City, said they knew little about the family.
A law enforcement official briefed on the investigation says the brother of the gunman has been "extremely cooperative" and is not under arrest.
The official tells The Associated Press that Ryan Lanza, of Hoboken, N.J., is still be being questioned but is not in custody and is not believed to have any connection to the school killings.
The official says Ryan Lanza's computers and phone records were being searched but only "in an abundance of caution." He says Ryan told authorities he had not been in touch with his brother in recent years.
Police say 27 people were killed in the shooting at a Connecticut elementary school, including the gunman, and one person died at another scene. The dead at the school include 20 children.
Young students crying and looking frightened were escorted by adults through a parking lot in a line after the shots rang out in Newtown.
The attack comes less than two weeks before Christmas and appears to be the nation's second-deadliest school shooting, exceeded only by the Virginia Tech massacre in 2007.