I'm going to be ignorant of the important details aforementioned by eetenor to simplify my response. The right move is based on exactly what the scenario is, but, I'll be assuming it's a relatively normal bubble structure as to give general advice in similar situations.
One thing to consider is that lose players, although they are more likely to have worse hands, and still equally as likely to have good hands as everyone else. They tend to shove with both good and bad hands. Thank being said, I think a lot of his range would still beat ATs, so you have to consider for yourself how wide his range is and decide based off of that, whether or not to call. If you're unsure, in this situation. In this situation, personally, I would advise a fold since betting under the gun suggests your range is really strong, and thusly, the cut off likely had cards at the top of his range.
Another thing to take into consideration the fact that you cover the other player's stack. He's aware of the fact that you could knock him out the tournament and, might even being using his notoriously wide range to provoke more calls from worse hands. I'm betting in this spot he has you beat.
