Campos went to check on a door alarm that had been set off.
And this was prior to the start of the shooting.
I don’t think the windows had been broken when Campos arrived.
Key here, is WHAT door was alarmed. I don't think it was the room door. Guests will often leave the room door ajar for various reasons. When I would go to a resort hotel with other families, we would get rooms next to each other, and the kids would go back and forth from one room to another, to join the group watching TV in room A, or the group playing video games in B.
Now, if the STAIRWAY door was propped ajar, that would be a violation of fire codes, and would merit checking.