NEWTOWN, Conn. - Connecticut state police said a teacher's son walked into a school and killed 26 people, including 20 children, before turning the gun on himself.
Six adults including the gunman's mother were among those killed in the school. The gunman then took his own life inside a classroom.
One additional adult was killed at a secondary scene. Media reports identified this additional adult as the gunman's father.
The Associated Press reported that the gunman's brother is being held by law enforcement.
The elementary shooting is being called "a tragedy of epic proportions."
The shooting was reported Friday morning at 7:30 MT at Sandy Hook Elementary School in Newtown, in western Connecticut. A SWAT team was among the throngs of police to respond including on-duty and off-duty state police officers.
A parent who was inside the school at the time of the attack told CNN she heard what sounded like at least 100 rounds being fired. Police said that the shooting occurred in one section of the school and only in two rooms.
Sandy Hook Elementary School has 450 students in kindergarten through 4th grade, making the kids in the school between 5 and 10 years old.
Most of the victims came from the mother's kindergarten classroom, ABC News reported.
Gunman identified as Adam Lanza
The gunman in this mass shooting is being identified by the Associated Press and other media agencies as Adam Lanza, 20.
Several media agencies, including the Associated Press, originally identified the gunman as Ryan Lanza based on information from unidentified sources. Agencies are now retracting that report based on the new information.
The AP said the information in their earlier report was from a law enforcement official who had mistakenly transposed the brothers' first names.
One of the AP's sources said Adam Lanza is dead from a self-inflicted gunshot wound.
Injured taken to nearby hospital
In addition to the dead, it's not clear how many others were injured in the shooting. An ambulance dispatcher said a teacher was shot in the foot and was taken to Danbury hospital.
Danbury Hospital said it treated three people. Danbury Mayor Mark Boughton told WABC the three victims in hospital are in “very serious condition.”