My nephew is gonna spend the rest of his life in a mental hospital

This happened a while ago but I recently started talking to my nephew and I'm going to go see him. My nephew killed my sister and I can't say she didn't deserve it. She was extremely abusive towards him. He suffered a lot of brain damage for her abuse and more. We called CPS but nothing really came of it. He started to slowly lose his mind in highschool and people noticed his sense of reality changing and when he got strong enough he started throwing the abuse right back at my sister and abused her and voices in his head were telling him to kill her. And he ran away one day and he warned my sister that she had the police bring him back he was going to kill and torture her and she had the police bring him back. And the next day he started a fire and barricaded her door and let the house burn. There were several psyche evaluations done on him and also going into his CPE cases of the abuse and his brain injuries from her abuse. His dad got him a really good lawyer and he was seen criminally insane. He was 17 when he murdered my sister and 18 when sentenced. Yes 24 now and I got to speak to him for the first time in a while. I plan on visiting him because he gets lonely but it is sad knowing he's gonna spend the rest of his life there and maybe this could have been prevented had he been removed from the home. It's sad knowing the little boy he used to be and how far gone he is now. Even talking to him over the phone he's completely out of his mind. But I hope I can offer him some piece of mind by seeing me.