Screenshot of local news coverage. (Michael Juliani)

UPDATE: NBC News reported the gunman has been identified as 20-year-old Adam Lanza of New Jersey. His mother Nancy, a kindgarten teacher, was among those he killed inside the elementary school. 

Connecticut State Police spokesman Lt. Paul Vance told reporters during a press conference this morning, "The shooter is deceased inside the building. The public is not in danger."

Adam's brother Ryan, whom authorities originally thought was the shooter, told police Adam has a history of mental health issues.

A shooting at an elementary school in Connecticut has left at least 27 people dead, including 18 children, according to the Associated Press.

CNN has video feed from the scene, including interviews with survivors.   

A law enforcement official said the shooter was a 20-year-old man with ties to the school, according to the AP.  One of the guns he used was a .223-caliber rifle.

The gunman was reportedly killed at the school, Sandy Hook Elementary in Newtown.

Reach Executive Producers Michael Juliani and Catherine Green.