Is the second LEO saying "Get the jaw?"
Either way, did what had to be done.
Grabbing the jaw hard (hand in mouth and fingers underneath) is one technique albeit a last resort technique to stop a dog from momentarily from biting, long enough to get out the pistol, OC, taser, Asp, radio, etc. We "practiced" on LEO dogs using "soft hands" so not to hurt them (or more so no not piss them off so that they did bite).
FWIW, if a dog ever comes after you and you are defenseless, knowing that the dog is trying to get a hold on you and eventually get your neck (yes, they are smart enough to go after you neck if they can), gather enough of your bravery and inner strength and give them your "weak arm" to grab and then get ready to start gouging eyes, pulling ears, anything to cause it pain and injury. Yell and scream and make as much noise as possible. Find anything you can to use as a weapon (rock, shovel, pen/pencil, twig, etc). What ever you do not let it knock you over.