[ The question earns Serpico a look that suggests that Bolin thinks the answer is obvious. Which he does. ]

You suddenly showed up in my room without warning. I thought some crazy person had broken in.

[ He likely should've known better. And really, it's not much of an excuse for attacking Serpico, especially with such force. Then again - it's not as though Bolin had reached for his weapon, at most he'd slapped the stranger a few times. Being in a state of undress had probably made him nervous and defensive. ]

Sorry about that I guess. It won't happen again.