Had to do that once with the little Sig P238. Back of the head. Poor young 2x2 had this open gash on the side of his hide. Wasn't getting up. His eyes had that wide-open out-of-it look. The mouth open panting in shock.
Ugh... and then while I was pulled over on side of the road, getting out the weapon from the locked case.... some cars coming past oddly slowed to a stop, and then tried to proceed by, I'd have presumed cautiously, but no! This moron in a compact car oddly was giving too wide of a berth to my vehicle, which was completely off the asphalt... and this yahoo goes and freaking partially runs over the damn things extended leg! Ugh.. that sound!!! I remember being real upset that this bast@rd would be that stupid.
He gets a burst of adrenalin and limps over to the tall grass on side of road then flops back over on side again.
Apparently one of the nearby rich-people ranch-style homes was having a wedding reception or something. This guy who was driving a "Party Bus" van had stopped on the other side of the road with his bus/van and turned on his hazards so somebody wouldn't come flying down the road and potentially hit him again, possibly causing an accident and injuring folks as well.
It's always a somber thing when you have to be the guy to do the coup de grace.