I suspect the copycat effect is a large part of it: https://en.wikipedia.org/wiki/Mass_shooting_contagion

The media has historically, starting with Columbine, been extremely irresponsible when it comes to school shootings, showing little of the discretion that it does when it comes to youth suicide (for which they've adopted professional standards informed by CDC, WHO, etc. recommendations: https://afsp.org/ethicalreporting/), to the point that it's given perpetrators fame that's endured decades after their demise: https://www.nytimes.com/2018/05/30/us/school-shootings-colum...

And they're doing this not just out of recklessness, but out of a pretty clear bias and desire to leverage these events to produce support for gun control.