This sounded odd because the fire door Paddock secured shut with a plate and screws was the next door from his room, not a few doors down.
However, a comment from a guest on a travel website that was reposted to Reddit said Mandalay Bay does indeed have an alarm that goes off if a hotel room door is open for a few minutes:
As Security explained to me when my statement was taken, they (Security) have the only master keys in the house. If the door was ajar for more than 3 to 5 minutes, they would have been alerted through a system called Hot Sauce prompting a response. This alarm is audible so I would have heard it as well since I was up for an hour after I returned. There are no cameras in the hotel hallways as it is an invasion of privacy according to Security. If you must, deadbolt your door, put your valuables in the safe, or stuff the cash under your mattress. My experience seems like an inside job since there is no other explanation on how my suite could have been breached.
(Also, numerous complaints of theft, suspicion falling on hotel employees. See https://www.reddit.com/r/conspiracy/comments/75jsh4/what_is_mandalay_bay_hotel_like_from_their_guests/)
So maybe Campos was alerted to an open hotel door somewhere on that corridor as was first said, and then heard drilling and as he moved toward Paddock's end of the corridor Paddock fired at him through the door, hitting him on the front right thigh, and Campos immediately hopped into a recessed door shielding himself, until he saw the maintenance guy Schuck.
So that leaves the question, how did the hotel know the fire door next to Paddock was screwed shut? Schuck said he was told to check out a stuck fire door and came down from another wing on a higher floor to do so.
Paddock definitely was not a pro. A pro would have baited Campos in and shot him dead inside his room and then kept on doing his work.
Shooting through the door makes no sense at all to me. This is ridiculous. Way to alert everyone around. It does not add up.
I’ll just mention this as a possibility: given the description of brazen thefts pointing to hotel staff in the comments by guests, perhaps Campos and maybe Schuck as well are part of a ring of hotel staff that steals from hotel rooms. One guy notices when guests have left the room, and uses his master key to slip in and have a quick look for obvious valuables, while someone else acts as lookout.
This might explain why the story has shifted so much as to what Campos was doing and why the low profile and no interviews. We didn’t even know about the existence of the maintenance guy for a week.
Surely, maintenance and housekeeping have master keys. The maintenance man left the floor to give his master key to his supervisor so the supervisor could give it to the cops. Why wouldn't the maintenance supervisor have a master key? No one's story makes any sense.
Both Campos and Shuck were sent to investigate an open emergency door because it would take two people to shut it and they were sent independently?
They send the building engineer up to the 32nd floor to investigate an open emergency door, as if he had nothing better to do and they don’t use lower ranked personnel for that?