The guy shot through the door and injured a security guard as they approached the room and then he killed himself. They walked in and found the guns, the shells, the dead perp and two broke windows ... and you think the shots came from somewhere else because you can't identify the 32nd floor windows based on a cell phone video? :-)
NO, I believe there was more than one shooter.
Also, why shoot yourself. You just shot hundreds of people, why not take a bunch of cops with you by shooting through the wall. He has enough rounds to shoot a new door in the wall. Hell, he has enough to shoot the whole wall down.
Why shoot yourself before you took some sops with you?