The problem I see isn't keeping a steady shot under stress, it's that he set up a shooting position not conducive to engaging an approaching target. And based on the bag setup I'm assuming that wasn't done in the heat of battle but at a time where he could have given some forethought to engagement angles. Hell, I give more forethought to that when setting up in a new deer stand for the evening.
Edit: although keeping a steady shot under stress is also a factor, and something I would expect an experienced professional to be able to do a far better job at than myself in this scenario.
Edit: although keeping a steady shot under stress is also a factor, and something I would expect an experienced professional to be able to do a far better job at than myself in this scenario.