Lets suppose you (Martin) park your car somewhere and leave it there. When you come back, out of the blue, you see a big scratch on your car’s surface. You have your friend with you who you stand on ceremony with him and cannot let off your steam by using bad language and swear words, but you would like to express your sentiments. I need to know what Americans use to describe the person who has scratched the car in the following scenario; (the only choice which comes to my mind is "so-and-so", but I doubt if I can use it in the following scenario in this way or not:
Friend: Wow, look Martin! Someone has scratched your car
Martin: Oh, no! Which so-and-so has done it?