Hello agoonie, welcome to PC!

Before getting a stranger involved (professor from uni) it it possible to get someone in the family to discuss this with him? It might be more effective that way.

Have you tried approaching the subject when he's not upset. "Uncle X, I don't mean to be disrespectful, but I'd really like to discuss what happened the other day. I don't understand what I did to make you so angry and how do we prevent this in the future?"