Another consideration was the police were not sure the shooter was still in the room.
They had the hotel room covered, there was no more shooting so they methodically sealed the building, searched floor by floor to see if the shooter was trying to escape while simultaneously evacuating the people from their rooms to safety.
There was a better than even chance that the shooter had a bomb in his room set to detonate when they tried to enter the room, which could have taken out a large section of the building