Who is it from?
Do you think he knows this person sent it? does he know the person?
How sure are you that it's cocaine?
What made you open the mail?
Has your son done drugs or been involved with them in any way?
There's no way to really know if it's cocaine if you are not familiar with it, it could be baby powder. If you look at it and it actually looks like powder, then it probably isn't cocaine. Cocaine looks more flaky, scaly and iridescent. There are so many aspects to this, there's not really any one answer. There's no way to know if your son knows this person or if they may be trying to set him up or hurt him. I would start out by asking your son who it is. If he says he doesn't know who it is, then perhaps he won't mind if you take the pkg to the police department. If he really doesn't know this person, I would take it to the police department, because the person could be trying to set him up.
If your son admits knowing this person, you'll need to find out if it's an adult or another teen. If it's another teen, I would want to get the other parents involved and get some type of intervention for both of them, perhaps make them do some type of community service, or get them into a program. If it's an adult, I would more than likely contact the police.
I welcome your thoughts, let me know if you want to talk more