Looks like caucasian

"How's Mouse?" Thomas asked.
"Leg's hurt," I said.
"Took one hell of a shot to do it," he noted.
"That's why I left him back there," I said. "Could be he's pushing his luck. Besides, he can help Forthill keep an eye on the kids."
"Uh-huh," Thomas said. "Am I the only one who is starting to think that maybe Mouse is something special?"
"Always thought that," I said.
"I wonder if he's an actual breed."
Charity glanced over her shoulder and said, "He looks something like a Caucasian."
"Impossible," I said. "He has rhythm and he can dance."
Charity shook her head and said, "It's a dog bred by the Soviet Union in the Caucasus Mountains for use in secured military installations. It's one of the only breeds that grows so large. But they tend to be a great deal more aggressive than your dog."
"Oh, he's aggressive enough for anybody, when he needs to be," I said.


Proven Guilty Chapter 33, Page 260