Mark Hunter: You see, feeling screwed up in a screwed up place in a screwed up time does not mean you are screwed up, if you catch my drift.
Hard Harry: Sometimes being young is less fun than being dead.
Mark Hunter: I mean, if I knew any thing about love, I would be out there making it, instead of sitting in here talking to you guys.
Chosen answer: Well, with no actual scene where he confesses, it's left up to us to wonder. Personally, I find it unlikely that he'd actually admit the whole thing to his parents, but they're not stupid and already had their suspicions, so the lack of any great surprise on his father's part isn't unreasonable. You also have to remember that Mark's voice changer had already broken before they drove down to the crowd - his father would have easily recognised his voice before his actual arrival, giving him a certain amount of time to get through the initial shock.
Tailkinker