There are self-help books written for seemingly every aberration of human experience: for alcoholics and opiate abusers; for widows; rape victims, gambling addicts, and anorexics; for the parents of children with disabilities; for the sufferers of acne and shopping compulsions; for cancer survivors; asexuals, and people who just aren't that happy and don't know why. But there are no self-help books for anyone who has accidentally killed another person. An exhaustive search yielded no research on such people, and nothing in the way of therapeutic protocols, publicly listed support groups, or therapists who specialize in their treatment.
Alice Gregory, "The Sorrow and the Shame of the Accidental Killer: How Do You Live After Unintentionally Causing a Death?" Annals of Psychology, September 18, 2017