Maybe there was two long guns in the trunk, and this only shows them removing the second one.
Aerial of police finding a loaded long gun in the trunk of a car in the school parking lot appears to be a shotgun. This occurred hours after law enforcement sources already confirmed that they found a Bushmaster AR-15 in his trunk. .223 shells were found at the scene. Who was shooting the .223 inside the school then? From the NBC News Connecticut live feed on 12/14/12.
"A Sig Sauer handgun and a Glock handgun were used in the slaying and .223 shell casings -- a round used in a semi-automatic military style rifle -- were also found at the scene. "