What is the common thread between Mass Shooters ?

What is the common thread between these Mass Shooters? Mass shootings haunt our country's collective conscience. Every breaking news alert that surfaced around the country filled people with sorrow, dread, and rage at the innumerable acts of avoidable violence occurring in schools, churches, parks, supermarkets, and other locations where people go about their daily lives. Is there a way to stop these shootings? What have psychologists and medical professionals lately revealed, and what link unites all mass shooters? What information has Big Pharma, the courts, and the media not given you?