The shooter came out the door of his suite, and shot someone in the hallway. There being no place to use for cover on the hallway, the normal officers had no choice but to hold in place and wait for swat.
Otherwise, I agree with you.
Also, the mass killer stopped shooting after he shot through the door. That is probably when he committed suicide.
So there was not as much urgency to blast the door down. The shooting had already stopped.