I have a friend who is a K-9 officer. They are there to protect the officer and are pretty fast. He has to worry about keeping the police from killing him while he is shooting the dog. Not likely that he is that good of a shot.
I hope that's the case. I don't want to see the dog sent over to "divert" his attention, only to have the scumbag shoot the dog.
How about a mechanical suicide dog? They could send it out to the van by remote and threaten to blow it up if the perp doesn't leave the van now.