My first premise shouldn't find too much resistance: Liberals for the most part are in favor of gun control and thus when regular Americans shoot shit up like Sandy Hook or Virginia Tech, they push the necessity of gun control narrative super hard. Conservatives on the other hand defend these incidents as mental health issues rather than gun control. They much rather focus on terrorism, particularly the foreign kind as it plays into their gamut of core issues like illegal immigration and neoconservative aggressive foreign policy. So when
This brings me to my second premise, which is a bit more arguable: terrorism is code word for Islamic violence. If we define terrorism as violence upon a civilian population or infrastructure to deliver a social or political message, V Tech Cho's face should be next to these two people. Sure they had different messages to send, but these mass shooters didn't do it for the money or any rational reasons. They did it to send a message (Joker style) about what they perceive as unfair or unjust and how violence was the only way for them to make the world notice.
My last premise: Muslims that get "radicalized," particularly those who grew up in the West, such as the Boston marathon bomber brothers (I hate running too, but these guys were on another level), do so because they felt oppressed by Western society. Whether it is the constant meddling in the Middle East by Western governments, first Britain, then US (which has occurred since WWI), casual racism in day to day life, or even the plight of Palestine, all of these contribute to a simmering anger towards the West. But this is unguided and without guidance, it just smoulders, However, when they take trips and talk with influential and charismatic extremists (many of them funded by Saudi Arabia, which in turn funded by the...West) the rage channels into actionable violence.
Believe it or not, this is Cho and Rodger and all these other mass shooters in a nutshell, except instead of grievance against the West, it's grievance against girls and other guys who have no trouble attracting them. They feel the same injustice and oppression and it simmers inside of them a similar rage. All it takes is some internet forums (sound familiar?) to get "radicalized" to further fuel this hatred when eventually it explodes in violence.
This is narcissistic rage in a nutshell: you believe the world should work one way (Middle East should not be pushed around by the West/girls should be attracted to me) and these ideas get so ingrained in your identity and self that when the real world contradicts this fantastical construct, it also damages your sense of self. These narcissistic injuries pile up and with just a little bit of guidance, becomes fuel for incredible violence. Unfortunately, this kind of terrorism is incredibly difficult to stop. Unlike a bank robber who knows robbing a bank is wrong, these people firmly believe they are doing nothing more than righting a wrong. Ironically, our current response of shaming the other side--conservatives using terrorist attacks to bash soft liberals and liberals using mass shootings to bash gun nut conservatives deepens this animosity and schism, which leads to further alienation and radicalization as certain individuals feel the uselessness of talking it out. The first step in curing any illness is recognizing that you have one. Until we recognize the issue is a social one born out of the lack of empathy, these attacks will continue.