Parents - how would you handle this situation?

I walked in on my daughter (17) having with her boyfriend (19). I yelled: "Finish up, then get the hell out." She seems mad at me, but I cannot be sure because she's too embarred to talk to me at the moment. Her boyfriend is a good man, but she isn't quite legal yet. What would you have done? And what should I do now? I'm a single father, so I am in charge of whatever proceedings are to be taken.