https://en.wikipedia.org/wiki/School_shooting
While it may be simplistic to assume a straightforward "profile", the study did find certain similarities among the perpetrators. "The researchers found that killers do not 'snap'. They plan. They acquire weapons. These children take a long, considered, public path toward violence."[5] Often times, shooters are inspired by past shootings as motivation for the method of executing these attacks from the guns to purchase down to the what to wear during the attack. [6]Princeton's Katherine Newman has found that, far from being "loners", the perpetrators are "joiners" whose attempts at social integration fail, and that they let their thinking and even their plans be known, sometimes frequently over long periods of time. In addition, psychologist Peter Langman has noted that school shooters typically fall into one (or occasionally two) of three categories: psychopathic, psychotic, or traumatized.
Rush was discussing that immediately after the incident the media was claiming that the shooter was bullied. He was asking who was bullying him and why aren't they still talking about it.