Nearly three times as many people die in school mass shootings when an armed officer is present. That's the finding of a study of every case since 1980, led by Hamline University professor Dr. Jillian Peterson.

Dr. Peterson joins Dave Ross to discuss why more weapons means more violence, even the hands of "the good guys," what to expect when kids are back in school after a year of pandemic stress, isolation and minimal socialization, and what prevention looks like before we reach the point of barricading classroom doors.