And I concur that you need to examine your hiring process to prevent it from happening again.
Our hiring process is incredibly rigorous and definitely gets us the best people most of the time.
It involves a workflow management system that hides people's input from each other until decision time. We each interview the candidate on various topics separately, then write up our impressions and vote on a scale from 1 to 4 (1 = hell yes, 2 = yes, 3 = no, 4 = hell no). It takes minimum of 2 phone interviews to get in the door for a face to face. Once in, a team of 6 people are given areas of focus and each gets an hour with the candidate (one of the hours is typically lunch - just a chat and get to know you). One interviewer is a subject expert who is focused on making sure that this person is better than at least half the people we have so far. If they are not better than average its a no-hire.
Once all impressions are written up and votes are in, a meeting is held and all votes/write ups are revealed. If one person is adamant against the person, then its no hire. Usually most people agree or abstain. Occasionally discussions ensue where we work at coming to consensus - kind of like a jury.
I realize it is resource intensive and probably not practical at a smaller company, but you should have at least 2 people interview and only hire when they agree. I have occasionally thought a candidate was a good fit and only when I heard other people's impressions did I realize that I'd overlooked something important.