Flush To Judgment

At my boyfriend's recent high school alumni gathering, it came to light that he had bullied a student (holding his head in the toilet, etc.). We've been together for almost two years and have discussed marriage. However, I'm truly unsettled that he was capable of committing such awful acts. It makes me feel that I no longer truly know who he is. He claims he's an entirely different person and could never do such a thing today. How much weight should I give this?

--Disturbed

Comforting sayings...