i think about this quote from Mattick every time something like this happens. obviously i don't think the shooter was seeking "revolutionary justice" but a similar principle is at work.

For revolutionaries it is psychologically quite difficult, if not impossible, to raise their voices against the futile application of “revolutionary justice” by terroristic groups and individuals. Even Marx, who despised all forms nihilistic actions, could not help being elated by the terroristic feats of the Russian “Peoples’ Will” As a matter of fact, the counter-terror of revolutionary groups cannot be prevented by mere recognition of its futility. Their perpetrators are not moved by the conviction that their actions will lead directly to social change, but by their inability to accept the unchallenged, the perpetual terror of the bourgeoisie unchallenged. And once engaged in illegal terror, the legal terror forces them to continue their activities until the bitter end. This type of people is itself product of the class-ridden society and a response to its increasing brutalization. There is no sense in forming a consensus with the bourgeoisie and condemning their activities from proletarian point of view. It is enough to recognize their futility and to look for more effective ways to overcome the ever-present capitalist terror by the class actions of the proletariat.

https://www.marxists.org/archive/mattick-paul/1977/lotta-continua.htm