Apparently he bought the gun and ammo from a sporting goods store outside of his state. So he bought the ammo already loaded and set. Which means, if he engraved it post delivery.

Given he didn't have the tools to empty and refill, how the fuck did he do that?

Also, those engravings are too on the nose propaganda like how tf did they know the arrows means to " call in a bomb in helldivers 2". Could have been Hadoken or something like infinite cash in GTA 1.

So imo construct, and it's done to entice Gen Z into general violence...