answer:We can only be accountable for our own actions, and have little or no control over others. I think your discomfort might be coming from the fear of how this person might treat you or others close to you – given what you’ve described as callous treatment of someone close to him. This is going to make you cautious, as it would anyone. Decide how important a “friendship” is with this person. Is he someone you need to work with, or someone you want to have a friendship beyond a professional affiliation? If you decide on friendship then tell him how you feel – that what he did was rotten and you didn’t like it. If you decide he is only going to be a professional colleague then don’t bother getting it all out on the table because it’s not worth your emotional energy and it will make your professional collaborations with him uncomfortable. Good luck!