Police stand guard at the entrance to Sandy Hook School
The father and older brother of the gunman who was blamed for the Connecticut school shooting were being questioned by authorities but are not suspects, a law enforcement source tells PEOPLE.
The Associated Press reports that the gunman has been identified as 20-year-old Adam Lanza
His unidentified father, who lives in New York City, and his older brother, Ryan, 24, of Hoboken, N.J., are "in shock," the law enforcement source tells PEOPLE.
They were questioned by the FBI in the Hoboken police station but "are not suspects, they have no involvement," the source says.
"Imagine the 24-year-old – he's lost his mother. Imagine the father, his son killed 20 kids," the source says."
As for Adam, "It looks like there's mental history there," the law enforcement source says.
Adam Lanza died at the scene of the shooting that killed 20 children and six adults at the Sandy Hook Elementary School in Newtown, Conn.
His mother, Nancy Lanza, was found dead at her home, according to CNN.
The source describes the weapons used by Lanza as "legitimate." According to CNN, Lanza used two hand guns that were registered to his mother and a rifle.
Adam's parents were no longer together, the source says.