From another source about the arrows:

Law enforcement officials revealed that Robinson inscribed the sequence up arrow, right arrow, down arrow, down arrow, down arrow on casings, which may be a reference to the co-op shooter Helldivers 2. In the game, the code triggers a 500KG bomb, one of the most destructive stratagems available to players.

So you know that RF Brain worm Jr is going to have a field day with this true or not.