He was an interesting dog.
A dog will typically lunge in, grab the snake in the middle and immediately shake the snake to pieces. I have seen them do it many times.
Old Smokey was different. He would lunge and jump back until he finally got in and would grab the snake right behind the head. He would clamp down sort of like a bulldog until the snake was dead. Then he would prance around with the snake in his mouth like he was proud of himself.
I used to have run reconnaissance in the backyard at night so they didn't snuff all my harmless colubrids who were out hunting.
Very smart snake-killer!