One of the first things I learned was to stay away from snapping turtles. They can be quite fast in attacking something and once they get a hold of whatever they grab at, it's screwed. They don't let go without the proper encouragement which usually involves cutting the head off or shooting the thing and then prying the jaws open if you still have what it grabbed in the first place.
As I said, I've no idea what happened, but I would just as easily believe that the turtle got that screwdriver as a result of it attacking someone as it was the result of being attacked by a future pedophile.
Best way to put that snapping turtle out of its misery is to cook it & eat it.
Lots youtube vids on preparing snapping turtle for the pot & they are not for the faint of heart.