Do your turn in your child to the police?

I caught my son bringing in a stop sign and a speed limit sign from his car late last night. He told me he had been on a scavenger hunt with a bunch of kids from his high school and that the street signs were on the list of items they had to get. Presumably there are a number of street signs missing around town this morning. I am so angry with him for being so stupid and putting people in such danger by taking a stop sign away from an intersection. I know he wasn’t thinking it through but he should have known better than this. I really let him have it last night and I can see that he understands that what he did was stupid and dangerous and immature. But now what do I do? At first I was thinking about turning him and his friends into the police for what they had done but my husband reminded me that this can be quite a serious crime and that in one case recently a teen was even charged with manslaughter after an accident occurred at an intersection that was missing a stolen stop sign. I don’t want him to get into really serious trouble for this but on the other hand, I don’t want to be complicit in his crime and teach him that bad actions don’t have real life consequences. Should I call the police on him? I am really torn about what to do?