A friend of mine is going to hire a hitman, how would you handle this situation?

So I have a friend, let’s call him “Jack”. Jack is in love with “Jill”. Jack and Jill were highschool sweethearts. Jill is currently married to a guy who beats her and cheats on her. Jill calls Jack once a week, and she tells him things like “I wish my husband were gone so we could be together”. This has motivated Jack to look into hiring someone to “deal” with her husband. (for some reason divorce is not an option I don’t know why). I’ve asked him things like: “would you really feel comfortable living with the guilt for what you’ve done” and his response is “I don’t care”. I can’t talk any sense into him, he says as soon as he settles the specifics and get’s the money together he’s going to move forward with this plan. I wish he just would have never told me about it, b/c now that I know somehow I feel involved. How would you handle this situation?