Newtown, Connecticut (CNN) -- Nearly 20 people died Friday in an elementary school shooting in Newtown, Connecticut, a law enforcement source with knowledge of the investigation told CNN.

Close to 30 of the dead at Sandy Hook Elementary School, 18-20 are children, the source said. At a news conference Friday afternoon, state police Lt. Paul Vance would say only that there had been "several fatalities."

A parent who was inside the school at the time of the attack said she heard what sounded like at least 100 rounds being fired. She said she saw two school employees who had died.

The shooter, in his late 20's has been named as Ryan Lanza is dead, a source with knowledge of the investigation told CNN's Susan Candiotti. Stay tuned for further updates.