My name is XXXXX XXXXX I'd be happy to answer your questions today. I'm sorry to hear that this is happening.
There is unfortunately no legal right to force the police to investigate or prosecute someone. If the BBs are causing injury, you can try again or talk to a superior police officer to see if they will take any action. Another option is to file harassment
charges, based on the fact that this person is engaging in a pattern of behavior that serves no legitimate purpose and is intended to put our grandsons in reasonable fear of being injured. It's a form of stalking, and it is illegal.
The law defines battery as any painful or unwelcome touching. Since the average person would consider being shot with plastic BBs to be an offensive touching, your grandsons may also have a civil claim for damages against the person who is shooting them. These cases are typically brought in Small Claims
court, and a parent or guardian may file suit on behalf of a minor. Try calling the court to see if they have forms that you can file to open a case.
Please rate my service positively before signing out, as this is the only way that I get credit for the time I spend helping you. I hope that you are 100% satisfied - otherwise, please reply so we can continue the conversation. Good luck.