Looks like 3 weapons in the school and one in his vehicle:
Conn. school shooter had 4 weapons - CBS News
As an example of the misinformation created by the media:
"A law enforcement source told CBS News that Adam Lanza had three weapons with him during the attack: Two handguns (a Sig Sauer and a Glock), and a
Bushmaster .223 assault rifle; spent shells were found in the school."
The Bushmaster .223 is a semi-automatic AR-15. Assault rifles by definition have select-fire capability (burst or fully automatic). As such,
not an assault rifle.