A press conference is expected to begin in a few minutes. We'll provide live coverage of developments.
Newtown, Connecticut, is about 120 kilometres northeast of New York City.
Sandy Hook Elementary School has students from kindergarten to fourth grade, which covers children roughly aged five to 10.
The suspected shooter was the father of a student there and was also killed, CBS News is reporting. The principal and school psychologist were among the dead, CNN reported.
Here's a quote from a parent with a child at Sandy Hook, via Reuters:
“It was horrendous,” said parent Brenda Lebinski, who rushed to the school where her daughter is in the third grade. “Everyone was in hysterics - parents, students. There were kids coming out of the school bloodied. I don’t know if they were shot, but they were bloodied.”
Here's an update from AFP on the White House response:
US President Barack Obama has been informed of a shooting rampage which reportedly killed 27 people at a Connecticut elementary school and is monitoring the situation, the White House said Friday.
Asked whether the outrage would push the issue of gun control up the president’s agenda, White House spokesman Jay Carney said: “I don’t think today is that day” to discuss usual Washington policy debates.
Many of the shootings took place in a kindergarten classroom, sources told The Hartford Courant.
The Courant also reported that an entire classroom is unaccounted for, citing sources.
Here's more on President Barack Obama's response to the school shooting, via The Associated Press:
The White House said President Barack Obama has “enormous sympathy for families that are affected” by the shooting at an elementary school in Connecticut.
Obama was briefed on the shooting Friday morning. Spokesman Jay Carney said the White House would “do everything we can to support state and local law enforcement.”
We're still waiting for a briefing by law enforcement authorities, who are expected to hold a press conference soon.
I've been monitoring some of the local Connecticut TV stations which are quoting CBS network sources: a possible second shooter is in custody. We can't independently confirm that. But that will be a key question.
Here's a bit of history on recent mass shootings in the U.S., via Reuters:
The United States has experienced a number of mass shooting rampages this year, most recently in Oregon, where a gunman opened fire at a shopping mall on Tuesday, killing two people and then himself.
The deadliest attack came in July at a midnight screening of a Batman film in Colorado that killed 12 people and wounded 58.
Just another couple of details being shared on Connecticut local TV: the state government says it does not have enough medical examiners and is asking help from neighbouring states. Also: shortly after the shooting, state authorities sent out a radio call asking that all state troopers on duty respond to the shooting; shortly after, the radio call went out that all off-duty state troopers respond to the call.
Here's an eyewitness report from a boy at the school:
"We heard lots of bangs," the boy told a local television station, saying he thought it was the custodian. He said the students sat down by the wall, and the police ran in and asked if the shooter was there. The children were then ushered to a closet in the gym.
Here's more on the alleged gunman:
The alleged attacker is a 24-year-old man who was armed with four weapons and a bullet-proof vest, WABC reported.
Stephen Delguidice is a parent whose 8 year old child was in the school. Here are some details his daughter passed on - and that he shared with CBS TV: the loudspeaker came on, children in the class and the teacher could hear “cursing”, the teacher told kids to get in the corner and locked the door.
Police found two adults alive and hiding in a closet just an hour or so ago, CBS reported
We're getting conflicting reports about the age of the alleged shooter. The Associated Press says he's 20 years old, while an ABC affiliate says he's 24.
“I’m not sure why the school system was on at the time,” said Stephen Delguidice, parent of an 8 year old who survived today's mass shooting during an interview with CBS. Mr. Delguidice telling the interviewer that it may have been that some turned on the speaker system to capture some of the argument between the school principal and the shooter - and this may have saved lives, the parent says.
AP says the alleged gunman had ties to the school, without elaborating.
A press conference is just beginning now.
A representative for Governor Dan Molloy says he is "horrified" by what happened and is now meeting with families.
A State Police Lieutenant says the call came in shortly after 9:30, and then asked for assistance from surrounding police departments.
The lieutenant says police quickly entered the school to look for the shooter and began evacuating students and staff.
"There were several fatalities at the scene, both students and staff," the police officer says, declining to elaborate until next of kin are notified.
The alleged gunman was found dead in the school, the police officer says.
The public is not in danger and the site has been secured, the police officer says.
The Governor's representative and police say more briefings will be held soon.
The press briefing is now over. Not much new information was released. Both the Governor's representative and police lieutenant said their focus remains on getting information to the families first.