The Associated Press
UPDATE: The gunman in the school shooting has been identified as Adam Lanza, 20. Earlier it was reported that his older brother Ryan Lanza was a suspect, but that was corrected.
A law enforcement official says the boys' mother, Nancy Lanza, works at the school as a teacher.
Speaking on condition of anonymity, the official said the suspect is dead from a self-inflicted gunshot wound.
The official spoke on the condition of anonymity because the source was not authorized to speak on the record about the developing criminal investigation.
School Massacre: Connecticut school shooting leaves dozens dead, most are kids
Shooting Suspect: Adam Lanza, 20, id'd as school shooting suspect
More on the suspect: Who is the Connecticut school shooter?
Facebook, Twitter: Social media reactions to Sandy Hook Elementary shooting
Obama reacts: Tearful president calls for action in school shooting
More: Photos as Obama reacts to school shootings
Prepare: What to do if you're caught in a school shooting
Share: Join the conversation on how to talk to you kids on our Facebook page
Photos: Sandy Hook Connecticut school shooting pictures
AP