Here's the shooter in a groyper halloween costume that his sister says is "from some meme": https://imgur.com/XeYByuq

"hey fascist! Catch! Up arrow, right arrow, three down arrow" is a video game reference from a video game called Helldivers 2 that groypers use all the time.

Every bullet casing had a different groyper meme on it. It's either a groyper or a really elaborate groyper false flag. Those are the only two options.

Acting like it's all a coincidence is just spreading disinfo. Thankfully the bots don't make it to HN very often, or this place would be a disaster.