GOOD GRIEF!
He had something like Ring cameras placed in and around the hallway so he could see anyone approaching in the hallway. That is how the security guard was shot. He is in a room at the end of a long hallway and can see what is happening in the entire hallway and most likely in the emergency stairwell that I’m sure is right there as well. Might that not explain some of the reports of “activity” on the 29th floor by the police communications?
Add to it, whenever anyone poked their face into the hallway, he was firing through the door to fend them off.
Now, considering that, just why in the H wold you just start to charge that door, especially when one officer is already down? I suspect they were trying to identify those little cameras he placed in that hallway and disabling them as they could to clear the path to the door and blow it as they did.
I suspect when he lost the last camera is when he offed himself.
So this 64 year old was not only shooting up the concert, but was monitoring hallways and picking off security guards?