We could be looking at one of the worst mass shootings in U.S. history, exceeded only by the Virginia Tech massacre in 2007.
The latest numbers are at least 27 people dead at an elementary school in Newtown, Conn., including 20 children.
Police say the body of the alleged shooter was found inside the elementary school. Unconfirmed reports say the shooter was Adam Lanza. (Police originally reported the shooter's name to news outlets as Ryan Lanza.)
James Alan Fox, a criminology professor at Northeastern University, says the U.S. averages 20 mass shooting deaths per year.
"Sandy Hook, I never thought would be in the news for anything, especially nationally," Heather McHuscker, a WBUR fundraising volunteer who grew up in the Connecticut town.
Joe Lieberman, author of "School Shooting," says shooters never think they're copycats.
"It gets in the media... they see themselves as an imitator," says Lieberman. "[But] all of the shooters this year have worn face masks and black gear."
Daniel Webster, the director of the Johns Hopkins Center for Gun Policy and Research, says it's clear that a lot of mass shootings involve young people:
The fact that it is so easy to acquire a firearm for anyone... probably explains why this country has a gun death rate so much higher than every other wealthy, developed nation.
The superintendent's office in Newtown said the district had locked down schools in Newtown, about 60 miles northeast of New York City. Schools in neighboring towns also were locked down as a precaution.
State police said Newtown Police called them around 9:40 a.m. A SWAT team was among the throngs of police to respond.
Photos from the scene showed young students, some crying, others looking visibly frightened, being escorted by adults through a parking lot in a line, hands on each other's shoulders.
Connecticut Gov. Dan Malloy was on the scene in Newtown.
The White house said President Obama has "enormous sympathy for the families that are affected" by the shooting at the school.
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."
The White House also said the FBI is supporting state and local law enforcement officials in Connecticut as they respond to and investigate the incident.
Carney wouldn't say whether the shooting would make gun control a higher priority on the president's agenda, but he said there would be a day for discussion on that policy issue.
This article was originally published on December 14, 2012.
This segment aired on December 14, 2012.