Stephen Paddock, the Las Vegas gunman, is an object lesson in this regard. As an affluent 64-year-old gambling enthusiast with no relevant criminal history, he bore little resemblance to the typical mass murderer, who tends to be an angry young man seething with resentment and with a history of violent outbursts. An exhaustive search of Mr. Paddocks life for a motive has so far turned up nothing. His brother, Eric, noted that Stephen was the least violent in the family during my childhood. I have no doubt that had Stephen Paddock seen a psychiatrist, he would not have raised suspicion of dangerousness.