It was found in the car. Not in the school.
Nope. It was a shotgun found in the trunk of the car as this video clearly shows:
http://www.youtube.com/watch?v=wLrxSgkqJQc
That's no AR-15.
The medical examiner also says the children were killed by .223 rounds. And the number of rounds fired attest to this. And, sadly, common sense also points to using the AR-15. Lanza was crazy but he wasn't stupid. If you were a deranged madman set on killing as many people as possible, would you leave your most effective weapon behind in the trunk of your car?
As much as I wish he didn't use an "assault" rifle, fact is he did. Denying this and/or trying to make this into some kind of conspriracy doesn't change things. Lanza used an AR-15 because he had one and because he wanted to kill everybody.