background. the one time honor roll student has no criminal history. >> his slate is pretty clean. and so there simply were not the same type of warning signs that we've seen in so many other shootings. >> reporter: today's rampage marks the 22nd school shooting this year. at least 35 people killed. that toll might be higher without the bravery shown inside those schools. >> most mass shootings take under five minutes. having resource officers on the scene to engage the shooter is going to save lives. >> shots fired at dixon high school. shots fired at dixon high school. >> reporter: this week, a 19-year-old opening fire near an illinois gym packed with students rehearsing for graduation. a school resource officer coming under fire before taking that student down. just last month students at santa fe high school in texas joined a walk to protest school gun violence. today, parkland senior emma gonzalez tweeting -- "you deserve more than thoughts and prayers, and after supporting us by walking out, we will be there to support you by raising up your voices." santa fe students and families