Every time there is a mass shooting, the media fall all over themselves to ask if mental health issues were involved. Let me answer that for this mass shooting, for all the past mass shootings, and all the future mass shootings: yes. Mentally healthy people do not go around shooting other people.
We (and I only loosely include myself in the group of mentally healthy people, except on this issue I am quite confident of myself) do not shoot people who insult us. We do not shoot people because our girlfriend or boyfriend broke up with us. We do not shoot people because they were texting in the theater or because they throw popcorn at us. We do not shoot our coworkers because they... well, for anything they did. We do not shoot kids because they are black or brown or gay or have droopy pants. We do not shoot people because they are mentally ill and homeless and don't respond to our orders.
There, was that so hard?