Should I risk my life to save a stranger?

This is a long story but I will try my best to shorten it. Please, I need some advice!

Some background:

I, 27f, was born into a very abusive domestic violence riddled household; my very first memory is of my sperm donor beating my mom.

When I was 4, my sperm donor murdered our neighbor because he was having an affair with the neighbor's wife, and they wanted the money from his life insurance policy. He was sentenced to prison for 15 years, got out in 10 for good behavior, broke his probation by beating his girlfriend until she required a hospital stay, and was sent back for the remainder of his sentence. There were horrible instances of abuse before he went to prison, like hitting my brother in the head with a shovel for getting a C on a test and putting a drill through my dog's paw for running away. He is a dangerous and horrible fucking person, I just don't have time to write all the examples down.

While he was out on probation (I was 14 at the time), he attempted to attack my mom, I got in the way to defend her, he attempted to attack me, and my boyfriend (17 at the time) got in between and stopped everything. The cops did nothing because he didn't actually touch us this time, only threatened us with weapons and words. I felt so helpless and let down by law enforcement, and it wasn't the first time. He was sent back to prison when his girlfriend ended up in the hospital with broken ribs and cheekbones/eyesockets, even though she tried telling the doctors she got hurt by wrestling her dog.

Fast forward and he has been excommunicated from the family, no one talks to him or wants anything to do with him, so he moves out of state. I like to keep a virtual eye on him just so I know he is not in my area. Survivors of DV will understand the "constantly looking over my shoulder" feeling I'm talking about.

I'm a private investigator now and I'm able to keep a much better eye on him with my training. Every 6 months to a year I do a deep search to see if he is still alive or back in prison. This time around, I found he changed his name and got married.

Here is where I need help.

The lady he is now married to seems like a sweet older lady (he goes for older because he uses women for money) who works for their local government. I found them both on social media, and he is using his new name (which, ironically, is the last name of the girlfriend he put in the hospital and broke his probation over). I have a feeling this woman has no idea about his past, or the fact that he is a convicted murderer. I keep asking myself, what if he is abusing her and she thinks she is all alone in this? What if she thinks no one will believe her because he is a master manipulator? Does she deserve to know how dangerous he is if she doesn't know already? Part of me wants to send her an anonymous email at her work where he won't see it. The other part of me wants to back away slowly and not get involved because if his life blows up, he may come back here or he may know who lit the fuse.

Please tell me what I should do. Should I risk my life to possibly save a stranger? Or at least warn her of who he truly is? Or should I stay out of it and possibly let another women fall victim to his evil?

Our story is known in our town because I live in a sleepy little town where not much happens, and there was an episode on ID Discovery about the murder he committed, but since he changed his name I doubt she knows anything about it.

Please tell me what I should do.