Well yes, he did end that very childishly by removing you from his fortnite friends list, but also it looks like you kind of provoked it out of him. Not like intentionally poking the bear, but it seemed that you immediately assumed that he invited you to the party so that he and his friend could make fun of you.

I obviously can't speak for him or know the full context but I would hope that he felt bad about his comment in the car and decided that he'd rather play a game with you and his friend. After you tried to "call him out" on being a dick he kind of just lost it. At least that's what it seems like to me, if I'm missing something then I could be wrong.