I suppose they have him on camera with her well before the tragic events, additionally I am almost positive every hallway isn’t a casino hotel is on camera ....l’d bet money on it
I've stayed at the Mandalay a number of times. There is at least a camera(dome) in the central area where all of the wings converge and the elevators are. Seems like they have domes spaced down the hallways too. Those halls are LONG, looks like his suite had a set of doors that looked down the entire hall.