Dogs And A Good Example Of Prey Drive

What would trigger cougars to mass kill these 15 Alpacas and not even eat them? 

Tiara told SFGATE that the mountain lions were not likely killing for sport, but due to their prey drive. “If they get into a pen and there’s multiple animals, they’re in kill mode, right? As long as there’s movement, they’re taking out every animal they can get,” he explained. “It’s just a predatory response.”

 Next question: why did the cougars kill the dog? And why do dogs attack cougars?