After Columbine, it was hard to imagine things getting much worse. 

At the time, the shooting at a Colorado high school was the deadliest school attack in US history. But then came Virginia Tech, and Sandy Hook.

With 13 victims dead, it was also one of the deadliest shootings overall. But then came San Bernardino, Orlando, Las Vegas and Sutherland Springs. In the 18 years since Columbine rocked America to its core, the country has seen so many more mass shootings that the attack isn't even among the 10 deadliest mass shootings in modern US history.