The weapon used was a military assault Bushmaster AR-15 rifle. I'm not sure of the magazine capacity but probably high number of rounds per minute.
He also had with him 2 handguns, one he used to kill himself when the cops came, and another shotgun. They said he had enough fire power to murder every child in that school, which they believe was his intent until he was interrupted by the quick response of the police. All these guns were legally purchased by his mother & in her name.
This school had a very advanced security system in place, as well as a plan for if the school is under attack. Most schools in the tri-state area now have a plan in place & taught to the teachers & practiced. The school was totally locked up at the time. He entered by shooting out a window & came in that way.