"But training and a real life situation can play out quite differently and humans are humans & sometimes just react instinctively."
I agree. It didn't look like the policeman had much time to weigh things up and he instinctively kicked the man's head when he lifted it off the ground.
I once read an interesting article that claimed the vast majority of what we consider to be decisions aren't actually decisions. MRI scans have shown that decisions are made before the thinking part of the brain is even engaged. Our brains then rationalise what's happened as a deliberate decision, rather than an instinctive act. That kick certainly looks like one of those events.