threats?

So my mom who's been in and out of my life just told me her ex BF who is a huge heroin addict and still part of a gang (vice lords) has been scoping out my area because he's trying to get back at her for leaving. Now my mom is also a huge heroin addict and begging me to come pick her up. I cannot do that as I am a nurse and on call today. I also do not want to drive two hours for her to not be there and put myself in that situation to get her in that neighborhood. I cannot also confirm what she says about her ex scoping out my area but I do know for a fact that he is crazy. 
Would you get a hold of the police? Or just leave it be? It's hard for me to take my own mother seriously in any case but I do know this man isn't right in the head. I've witness him beat her many times. I have seen him cut open couches because he thought "demons" we're in there. 
I'm so stressed out over this.