When news spread that a high-profile comedian was killed in a murder-suicide in 1998, the response was disbelief: Phil Hartman wasn't just famous for being funny. He was even better known for being a good-hearted guy. The shocking story behind the deaths of Hartman and his wife, Brynn, not only made international headlines, but it shook the entertainment industry and changed how people talked about substance abuse and mental health issues in America.