My daughter has been in contact with her father

I finally told my daughter who her father was. She had been asking for years and I always said I would tell her but honestly never planned to. She's 18 now. Her dad is a murdering. We only dated a short period of time and he was arrested shortly after I found out I was even pregnant. He was severely abused as a child within the church and he murdered 8 people. These 8 people were the people who either physically or sexually abused him. One thing I never mentioned in my original post about this is he also burnt down the church this all happened. But he basically went on a killing spree murdering the ones who hurt him. His whole childhood was dark. This was dark. It's why I protected my daughter by never telling her and I never told him that he had a daughter. Especially since he was sentenced to death which recently after near two decades got overturned. He has life in prison but he won't be executed. I do wish he could have gotten the help he needed so this didn't have to be the outcome. It's not that I feek bad for hiw abusers. It's that it's sad that someone who was innocent lost their mind.

Anyway I did tell my daughter and she was horrified and went on a deep search about him and everything. What I didn't know is she wrote him in and they had been exchanging letters. I found the letters in her room and went through them and I'm so worried. It's not awful. She just wanted to know his story. He told her. They exchange back and forth. She said she wished he could get out because in the end what he did saved other kids from being abused at that church and he told her that he's were he needs to be and opened up that he has killed IN PRISON! One was a pedo that was jacking it to Disney channel (gross) and he had killed another pedo and then it went from that to having a blood lust to kill people. It's not about revenge anymore after being there for so many years. At first it was revenge. Then he killed those pedophiles because he felt like he deserved it. Now he has killed because one of his cell mates annoyed him. He has a blood lust and told my daughter that there's no good in him anymore. My daughter was telling him she believes there is still some good in him. These letters were just hard to read. I can't tell my daughter she can't communicate with him anymore. After all she's 18 but this is too much for her. It's why I didn't want to tell her. I didn't want her to reach out to him and now she knows all this dark stuff