Am I too charitable or is it possible that this guy is actually just joking and entertaining themselves? I can't imagine someone being serious with these threats and at the same time typing out shoot shoot shoot. Maybe it is just a weird hobby. Like when people play the long chess games where they share a board in common space and just make a move every time they happen to pass by and be in the mood. Maybe this person pours themselves a cup of coffee every morning and goes to Wikipedia to do his morning revert.
There is some effect where people contribute often and wonderfully in their area of expertise but turn completely weird outside of it. Stuff like a doctor running into a historically notable alternative medicine topic.
If HN, Reddit, 4chan, Twitter, Youtube comments, etc have taught us anything it's that people who should be mature enough to know better will readily engage in "no u" type arguments like 14yo kids.