I think it is a tragedy and quite horrible that people were killed. I recall there being a similar thread on reddit (back in the days of r/SS before it was banned) and it discussed something similar. Anyways, I'm on board with the majority of people's opinions on this, that it is WRONG to take others who had nothing to do with those perpetrators' suffering. Now if they had gone after the people who are responsible for their woes, then it is a very gray area, it would all depend on a lot of variables, whether the responsible parties continued to cause trouble to them or suffering, and/or depending on what the responsible parties did. Note that I am not condoning vengeance or violence against anyone, just putting that out there as a gray area.
One thing that always baffled me was how people who took others with them aren't considered mentally ill or irrational, but evil and then hated through the public at large as well as media, yet when someone suicides or only took themselves out, it is seen as mentally ill, irrational, and depressed. It is almost as if someone who hurt others they aren't considered mentally ill, yet if they only hurt themselves they are considered mentally ill. Correct me if I'm wrong, or unless I'm not seeing things the right way. In short if someone commits mass murder, the public and the media often calls for punishment and condemnation, dismisses the fact of mental illness, but yet if the person only takes his/her own life, then public and media calls it 'mentally ill'. Both actions require cognitive planning and careful planning, as well as a level of rationality in order to execute, but one is mentally ill while the other one is just 'evil'. Doesn't make sense logically...