It's all about disproportionate force. You can't nearly kill someone for slapping you in the face and acting aggressively towards you, especially when you can simply run away.
This.
While the women were stupid for jumping the counter and trying to challenge him, he reacted with disproportionate force.
What we do know is that one of the women slapped him, and then both followed him behind the counter.
Those last couple whacks with the bar were questionable IMHO, but I don't have much sympathy for the 'victims' in this case.
"Questionable" doesn't even begin to describe it. It was clearly an overreaction. Then again, he being a person with a violent past, maybe it didn't seem anything like an overreaction to him.