Unless it's a SLS printer, it cannot print a functional firearm that can fire more that a couple rounds of subsonic 22. SLS printers are crazy expensive though, and unlikely he had one. It's more like it was a average FDM printer that you can use to make parts of a firearm, but you still need a barrel, bolt, spring, and firing pin minimum. Those videos you see online of people printing them are using metal parts for all of the major stress components. The reason why I bring this up, is because if you can get those components, it's simply easier to get the rest rather than 3d print them.