Parent who threatens to hurt self or others. Advice?

I have shared before with this group that my mother has cognitive issues from a stroke she suffered a couple of years ago. I have written her doctor several times and contacted APS on three separate occasions. Each and every time I am told that she seems fine and that unless she causes harm to herself or others that there is nothing I can do. Today I received a call from one of her neighbors that she is threatening to hurt herself or others with a gun. What am I supposed to do? I live 1,500 miles away from her. She and I have a very rocky relationship and she will not listen to me. I need advice....