A law enforcement official said the shooter, who is dead, is believed to be a father of one of the students at Sandy Hook Elementary School in Newtown. Authorities recovered a Glock and Sig Sauer 9mm handgun, but it was unclear who killed the shooter, who wore black combat garb and a military vest, according to information on Fox News.com.
An official with knowledge of the situation said the man, described as in his 20's, had two guns. The motive is not yet known.
Earlier reports of a second gunman are unconfirmed. The Connecticut Post reports that police are also questioning a handcuffed man in connection with the shooting. Witnesses told the newspaper he was led out of the woods by officers.
Shortly after 9:40 a.m., authorities reported that a shooter was in the main office of the school. A person in one room had "numerous gunshot wounds," police told the Hartford Courant.
A dispatcher at the Newtown Volunteer Ambulance Corps said a teacher was shot in the foot and taken to Danbury Hospital. Local news outlets also reported that the principal was among those shot.
Parent Lisa Procaccini told Fox News that her daughter was sitting in a classroom when she and others heard gun shots.
"She was in a small class -- a reading group and they started hearing bangs," Procaccini said. "Her teacher, and I’m grateful for this, rushed kids into the bathroom and locked the door. They told kids it was hammering and tried to keep them calm.”
"Children were crying," Procaccini said. "She did tell me about a little boy that was in a police officer’s arms, bleeding. I don’t know if she gets it."
The Bureau of Alcohol, Tobacco, Firearms and Explosives said two firearms were recovered from the scene.
President Obama was notified of the shooting around 10:30 am ET, White House officials said.
The Newtown School District has locked down schools as a preventive measure to ensure the safety of students and staff.
A statement on the district's website stated that afternoon kindergarten classes have been canceled.
The elementary school has close to 700 students.
Newtown is in Fairfield County, about 45 miles southwest of Hartford and 60 miles northeast of New York City.