There is only so much a person can take, however laid back and mild mannered they are, before they will snap and it sounds like this idiot had pushed you to the limit, no wonder you lost it and shouted out. He sounds like a childish little oik desperate for attention, I hope he thinks twice about targeting you now.
I think your aunt probably sums him up perfectly It sounds like shouting out seems to have made him think twice about how he acts around you now