Surprised while jerking off

I was in the sauna park again and I always get really hot there. I was really horny and went to the loo. Suddenly a sauna guest comes up behind me and surprises me while I'm wanking. But as I was totally horny anyway, I immediately started to suck his thick, long cock. And last but not least, I had to piss and just let my pee run into the urinal ;-).