If they haven't kicked your door in by now, I doubt if it is a LE "sting" operation. They want to catch you with the illegal goods before you have a chance to get rid of them. Calling the police, especially when specialized knowledge of gun parts is needed to determine if something is legal or not (even a FA bolt is legal 99% of the time under Fed law) is just going to cause all sorts of headaches for everyone involved, including you. If you are truly concerned it contains something illegal, remove the label and toss it in a dumpster far from your home.
Most likely someone just got the wrong address written down. Call UPS at their 800 number and tell them the package got delivered to the wrong person and you would like to return it to the sender. Ask if they can have a driver pick it up, either from your work or just leave it outside your door at home. They should not have a problem doing this.