Connecticut State Police are responding to reports of a shooting at an elementary school in the town of Newton that police sources say left 27 people dead.
Ryan Lanza was originally believed to have been responsible for the massacre at Sandy Hook Elementary School, one of the worst in U.S. history.
Now, several sources report that his brother, Adam Lanza, was the shooter.
Authorities said the gunman is dead. An official with knowledge of the situation told the Associated Press that the man apparently had two guns.
Earlier reports of a second shooter are unconfirmed at this time.
Shortly after 9:40 a.m., police reported that a shooter was in the main office of the school. A person in one room had "numerous gunshot wounds."
A dispatcher at the Newtown Volunteer Ambulance Corps said a teacher was shot in the foot and taken to Danbury Hospital; it's unclear if that was the only injury.
The Newtown School District has locked down schools as a preventive measure to ensure the safety of students and staff, state police spokesman Lt. Paul Vance said.
A number of personnel are on the scene to assist. A statement on the district's website stated that afternoon kindergarten classes have been canceled.
UPDATE, 12:57 p.m. EST: Police are now reporting multiple deaths, several wounded children and at least one injured teacher, according to the Hartford Courant.
Unconfirmed reports say that principal Dawn Hochsprung and a school psychologist were among those killed, according to a parent who claimed to witness the attack.
CBS reports that a student's father was the shooter at the school.
Local TV reports, along with the New York Times, claim that as many as 20 people may be dead from this tragedy. Our hearts go out to their families.
UPDATE, 1:33 p.m. EST: State police say that a SWAT team was among the enormous deployment of law enforcement officers who descended on the school.
At least one sharpshooter could be seen on the roof of the school.
Danbury Hospital said it was treating three patients from the shooting scene. The hospital, which is not far from the elementary school, said it was on lockdown.
Gov. Dannel P. Malloy arrived at the scene of the shooting.
The school, located among wooded hills and suburban tracts in Fairfield County, 12 miles east of Danbury, serves kindergarten through fourth grade.
The school has approximately 700 students.
UPDATE, 1:35 p.m. EST: At least 27 people have been killed, 18 children, among them, according to the AP.
UPDATE, 2:40 p.m. EST: The Times now confirms that a gunman killed 26 people, 18 of them children, and wounded seven others before killing himself.
The gunman, believed to be in his 20s, walked into a classroom where his mother was a teacher. He shot and killed her and then shot 18 students in the classroom.
He also shot seven other adults.The gunman then killed himself inside the school. The shooting ranks among the worst in recent United States history.
UPDATE, 3:08 p.m. EST: Ryan Lanza, 24, was identified as the shooter, but several reports now indicate that his brother, Adam Lanza, 20, was responsible.
Those sources say Ryan Lanza is being questioned by police but is not a suspect.