He's not necessarily savage. It's hard to control yourself in those situations.
When I was in high-school, some punks set off fireworks in the cafeteria, but everyone outside that area thought it was gun-fire and started panicking and running. I ran right along with them and had zero control. There was a girl that had fallen and I wanted to help her, but couldn't...
I mean, when you see a scary man with a machete that you think is going to murder you, your parasympathetic nervous system is going to take control and you aren't going to do **** .
He didn't use her as bait. He probably didn't even realize that he knocked her off of the dock until he calmed down.
People think about themselves in deadly situations. That's just how **** works.