In trouble for something passanger did.

I NEED to know what the best, worst and most likely thing that can happen to me are. I was driving on a dirt road and my friend has a BBgun and starts shooting traffic signs and mailboxes. A guy whos mailbox he shoots gets my licence plate and calles the cops. A while latter a cop sees me and pulls me over. My friend admits to shooting 3 mailboxes and I tell the cop that I warned him to stop shooting stuff and to put the gun away 3 times. The cop says I am in as much trouble as my friend because I didn't take the BB gun away from him. The cop says I will get a court date sent in the mail, and tells me to drop my friends off and go home. I'm 19 and my friend who had the BB gun is 17. I live in Michigan. I have never done anything wrong before. I am very scared PLEASE HELP ME.