That is a very interesting and challenging problem that you have on your hands. It is sad that a candidate can hold it together during business hours but engage

That is a very interesting and challenging problem that you have on your hands. It is sad that a candidate can hold it together during business hours but engages in anti-social behavior elsewhere that is indicative of mental or substance abuse issues. Your best bet, as a small business with limited resources, is to sever ties with this individual and use all police and legal resources available to you. The reason for this is arbitrary and stems from your liability as an employer to the safety of others, and to the office building's zoning laws. I was honestly in this exact same position a decade ago and I was able to stay out of everyone's way by sleeping in my car in the back of another corporation's parking lot. Bringing this behavior into the office shouldn't be acceptable for legal reasons, not personal ones.