It may sound like just some stupid kid, but these thing often escalate. The fact that he has contacted other women means that he at least knows where you work.
Berkeley PD has some info on stalkers and link to organizations that can provide more info.
Quote:
Tell the stalker "no" – once and only once – and never give the satisfaction of a reaction. The more you respond, the more the stalker will think his/her actions will get a response.
Have a witness with you if possible. Tell the stalker in no uncertain terms and don’t waste your energy trying to be polite. If you convey anything other than "NO WAY," the stalker will assume you mean, "keep trying."
Hope its just soem stupid kid, but I would check with the others who have gotten calls. If any of you start getting unexpected packages it may be more serious.