This is one of the harder things to keep a handle on, as, well, personalities don't always fit into narrow little boxes....Think about what the character would have done, and there you go. But think hard and deep about how the character would view the situation, etc.Then you'll have your answer.
If person A kills person B in a dumb and stupid manner and you have good in your alignment would you in RL laugh it off? If you wouldn't laugh it off RL...then why, when RPing your character would you laugh it off?