Taken at face value and considering the OP's reaction to what was going on, this strikes me as an evil act. As to whether or not the PC is evil, I don't know. I only have one snapshot of an incident and not any long term familiarity with that PC. Considering how the OP took it, it sounds like this was something out of character and a little off. So I don't think the PC goes around killing anyone with steel in their hands "just in case".
Since the whole thing was kind of glossed over and the game moved on, I'm guessing this really wasn't a big deal for the group (DM included). We don't know what kind of game the DM is running. Is it black and white, where the PC's are the heroes and anyone who opposes them or seeks to do them harm is evil? Is it a game that explores the moral complexities of the adventuring life, with shades of gray and tough moral decisions? It's entirely possible that the bar fight was just a fun spin on a combat encounter and not intended to have any consequences. Just an unusual fight and whatever happens, happens. Or it could be part of an ongoing narrative where the adventures explore the ideas of unchecked adventurer power and the impact on a community when one of their own dies. So I don't know what kind of game this is. Is it adventure and fighting with this being just another obstacle the party has to overcome? Is it part of a story that explores character psychology and has longer lasting consequences for everything the group does? Basically, what kind of game is it? Is this the kind of story where we don't care that Batman technically is committing assault and breaking and entering when he fights crime or is Batman wanted by the police for going too far? I've read both and they can both be good, but they have very different goals with their stories.
So really, what kind of game is the OP looking for? What does the group enjoy? If this is something that could lead to interesting future consequences and possible soul searching for the PC and they want that kind of game, run with it and say he did something evil. If people just want to get the party together and go raid some goblins and find cool treasure, don't worry about it. Without knowing your group and what you look for when you play, I can't really say if the PC is evil or even if it matters.