Why start shooting into the hallway before his rampage out the windows? It doesn’t sound like they were coming for him so why alert anybody before the deadly shooting.
Excellent question... did he figure that they were about to see the cameras on the service cart and they would be beating on his door anyway trying to find out what was going on? The question goes hand in hand with the one of why did he stop shooting after 10 minutes when he had lots of ammo left? And why did he arrive in LV with tons more ammo and other materials left in his vehicle that never got used?
He panicked? Dude was on drugs.