1) there was a magazine already laying in the hallway the first time he enters the building.
2) white walls and no signs of blood on them not even splatter the only blood seen was on the ground in puddles
3) the guy that runs at him is shot at blank range and no blood blowback or splatter a small hallway like that the walls would be a mess from just that shot
Shot out the windshield with a shotgun very important to keep that in mind it was a shotgun. If a rifle was shot out the windshield a small hole would be normal because it is safety glass. But a shotgun even if a slug was used would blow a huge hole in it. It looked like pressure from the barrel being almost against the side window not a projectile is what blew it out.