After you have acheived 7 consecutive kills without dying, you are rewarded with a Pack of Dogs. Multiple dogs will start to appear throughout the map, chasing down enemies and mauling them to death. Dogs are quite hard to defend against, as they attack in packs. Shooting them or knifing them will reward you with 3 points each. Only one pack of dogs can be on the map at the same time. Your are rewarded 10 points for releasing the dogs.
When you are under attack by a pack of dogs, it is best to run into any nearby lake or ocean, as the dogs will not come into the water. If there isn't any water available, try jumping on top of a box or ledge because the dogs usually don't jump that high.