2. You need to assess your culture. Is this one bad apple or is this something larger. The work hard, party hard, live in the office startup culture can be a breeding ground for this. Not that you can’t have this environment and succeed, but you need to understand it and put checks and safeguards in place. One option is to designate a sexual harassment rep and make sure everybody knows this person’s roll and that they can talk to them, possibly anonymously.
3. Talk to your female employee and let her know you have to do something. You can’t ignore it as that effects the company and thus everyone. Get her opinion about how much of a problem his continued presence in the office will be. She may not want him to be fired as she may feel partially responsible (not saying she is in any way, but we don’t know how she’ll feel).
4. Talk to the bizdev employee. Document the meeting and any outcomes or remediation. Is this a problem of just being junior and not yet having the ability to separate barroom behavior from the work place. Why did you hire this person? Are those qualities still there and does this person have potential? Only you know.
Talk to a lawyer, but remember, you are the leader, they are not. Walk through the steps and make the tough decision about what is best for everyone. Reactionary firings can be almost as negative on your culture (not your liability though) as doing nothing. Be the type of leader who talks to their people and tries to come to a decision that is best for everyone. Don’t be the leader who makes reactionary decisions behind closed doors.
Also, don’t talk about ‘kicking someones ass’. As a leader, this is almost as bad as calling someone a MILF. Step back from your emotions. After a decade in the military, part of it working in legal, I’ve seen a lot worse: rape, child porn, attempted murder, grand theft, fraud. While obnoxious, calling someone MILF is pretty far down on the scale. This makes it tougher in some ways since firing isn’t automatically the only response.