Mass shooters 'do not just snap': How to spot violent people — according to the FBI

Mass shooters don’t just snap — whether it’s changes to their behavior or personality, comments or jokes about self harm and violence, or obsessing over past mass shootings and perpetrators, they leave behind a trail of warning signs that can sometimes span years.

That’s according to Shohini Sinha, the special agent in charge of the Salt Lake City FBI Field Office, who briefed reporters Monday on the agency’s new Prevent Mass Violence campaign, which outlines the behavior often exhibited...