You might look at school shootings and think “Yes, obviously.” But two people who have been studying and participating in the movement for decades explain how its success isn’t obvious. This episode was produced by Jillian Weinberger, fact-checked by Laura Bullard, engineered by Paul Robert Mounsey, and edited by Sean Rameswaram, who also hosted. Transcript at vox.com/todayexplained   Support Today, Explained by making a financial contribution to Vox! bit.ly/givepodcasts Learn more about your ad choices. Visit podcastchoices.com/adchoices