Hi tetsuo13
and

I am really sorry what brought you here. Being menaced with rages by someone with a gun is scary! Sounds like your cousin has serious mental health problems.
I think you did the right thing to speak to family members and the police even if the outcome was not what you had expected.
What I can see, is you have to deal not only with him but also with his mom who is calling you everyday. What about validate her feelings and stay your ground that you would like to move on? Like: "I can feel your worries about how things are right now with cousin and me. I don't see any chance to sort it out by an email."
My advice with persons with N traits is try to avoid arguments. Which is sometimes not easy.
What did the cousin in the past week? Did he stay away from your warehouse?
Please stay in touch, tetsuo13
Surnia