You would have to write the letter as a cease and desist letter, not an order because that order is not allowed, generally speaking, unless it's from a court. You can certainly write them a cease and desist letter. I just gave you one example of a cease and desist letter. There are others available on the internet, and let me know if you want me to find another one for you. Leave out the laws from the other states. You can say that the stalking and harassment is against you and your mother or whoever else it affects.
If the behavior continues after sending the cease and desist letter by regular and certified mail, and I would say give it at least 1-2 weeks, then you can bring it to your local prosecutor or DA. If you want to bring it right away to the DA, you can try to do that. See if they will take the case right away and agree that you are entitled to a restraining order. There is no reason any of you need to put up with this.
You can see the DA or prosecutor without an attorney of your own if you'd like. I generally recommend an attorney for all court situations, but if the DA takes the case, you can talk to the DA and he or she will let you know if it's advisable for you to have an attorney present with you. You might want to have one to help you deal with the court, which is sometimes terrifying for non-lawyers, but that is up to you.
If you do a cease and desist letter, put in the letter what they are doing: contacting the apartment manager repeatedly, having her son in his official capacity as a police officer, in uniform, show up to intimidate you, etc. You can be as specific as you want to be. You may want to include as much information in the letter.
Again, if you want to bypass this step, call the DA's office, see if you can talk to the DA about what is going on, and see if you can get into court to get a restraining order against all these people who are causing the menacing, harassment and stalking that is going on here.
If you do the letter, call it a Cease and Desist Letter, not an Order. Only a Court can issue an Order.
I wish you the best of luck! If you have any follow-up questions, please feel free to send them to me via email or continue here. As long as it's part of the same issue, there's no additional charge unless it involves a lengthy answer on my part. I want you to feel free to contact me.