I need help about abuse

I ‘dated’ this guy, who used to beat the hell out of me and threaten me. I got out of this after almost a year, we were friends, I didn’t like him like that, but he basically forced me in it. I was scared so I went along with it until he pulled a knife on me for the 3rd time after beating me up. He did this because I tried to distance myself from him. Anyways it’s been a year since I’ve last spoken to him. However I see him walking occasionally and I have full blown panic attacks because of it, and also if something triggers me to certain memory’s.

So...I seen him yesterday holding hands with someone I went to school with. I tried to ignore it, and go on with my day. (I did have to pull over after due to my panic attack). I want to warn her, if she doesn’t already know how violent he can get. I don’t know if I should tho, because I’m afraid he’ll come after me.

Help :/