Was the AR used in the shooting or was it left in the car?
It was used...
The question that matters to me is was my AR used in the shooting, and the answer is no, it was not.
Have the police made their findings public yet?
No official police report public yet. We don't know but we did get tons of disinformation.
See this news vid report:
http://www.youtube.com/watch?v=IqpjJ6P-NSQ&feature=player_embedded#t=0s
CNN has an article about exactly which guns were used at Sandy Hook. Only one was left in the car and never used:
http://www.cnn.com/2012/12/18/us/connecticut-lanza-guns/index.html