I've seen hogs chase down and eat a live chicken. Not a pretty sight.
We had a freezer that broke down, and we had to get rid of about 100 lbs of rather questionable pork. We cooked it through over a fire and threw it in the pig pen. They went from playful and friendly farm animals to extremely violent wild animals in the blink of an eye. I was horrified (9 years old). It took my Dad a week to convince me to get back in the pen to feed the pigs. I never looked at them the same after that.
Pigs are omnivores, that's for sure.