I know this guy cheating on his wife ! help

So i used to work for this company i wont mention, but my boss male has had a wife for a long time. Recently like over the last 6 months to right around the time i left in January. I would see him screwing around with his assistant. I ended up seeing them out in public one night. There is a rule you cannot date or hangout with others from work. He also told another employee that he has tried “chocolate” one time when he went out of town for work (story short he was telling this girl he cheated or wanted people to think he cheated with a African American woman). I know he has at least been with the assistant because she would get weirded out when i would ask questions on certain things. I would like to reach out to her on facebook and tell her but i dont want to cause any trouble in my life. Please let me know what i should do to help this woman so if she wants to move on from this situation she can.