Oh good grief. Too long a day. That was supposed to be:
Would not all exits from the hotel be blocked?
He probably thought he had more time. The entire attack plan was to create chaos and confusion. People getting shot at all thought there were multiple shooters. That is why two open windows. He had the stairwell next to his door barricaded so he could walk down the hallway. That would get him to the elevators. Or to other tower wings in the hotel. He obviously wanted to get to his vehicle and expected them to eventually track him down. He had lots of ammo in car and explosives.