I thought i would feel better but I don't

My son died at the age of 15 over a year ago. What was originally thought that happen was him and his friend broke into my neighbors house and he shot them. My son was constantly in trouble. Constantly getting into fights. Stealing. Vandalism. So it made sense but the police investigated and things didn't make sense. My neighbor waited 4 hours to call the police after he shot them and he said it was because he was scared he shot 2 minors. There was class on the outside of the house which means the window was broken from the inside. And there were severe signs of sexual assault on both my son and his friend but no semen. So they suspected much more. His family harassed me saying that my son deserved to die for breaking into a poor old man's house and when he was found guilty they harassed me more. Shortly after he was found guilty he admitted to what he did and that they didn't break in. He SA'd them and then got scared they would tell and then killed them. I thought knowing the truth I can heal and move on but I actually feel worse. Because it's my fault. I should have been there to help. I should have tried harder to get him help for his issues because then maybe he would have been home safe. That man's family still harassed me. I have nightmares. Knowing the truth I feel has fuck me up. It's hard to even say my own child's name because I feel like I don't deserve to say his name because I failed him. The whole time he was probably hoping I would come save him and I didn't. I don't feel I even deserve the title mother anymore 💔