Bull
The shooter was identified because a fire alarm was set off in the shooters room from the burned gunpowder and the guest in the room below heard the activity.
A supersonic rifle bullet sounds like a jack hammer running even after being suppressed with a sound suppressor and would have been heard by everyone regardless
Indeed. But it nevertheless can be extremely difficult to identify the shooter's position.
Remember how long it took to catch the DC snipers? The police were looking for a white box truck for the longest time until they weren't.