Okay you can 3D print a lower for sure and maybe buy a slide and barrel using false information, but where do you buy the fire control group without going through an FFL?Do you buy buy it on the street illegally? If you are going to do that then why waste the time fabricating when you could just buy gun and silencer complete on the street? I just don’t see the logic and this guy certainly had the money to buy whatever he wanted without making some semi functional cockup.
There are literally hundreds of 3D printable designs for trigger groups on line. Google it.
What is odd about this, is that if the pistol and suppressor were 3D printed, it was likely for this specific target, not for something he intended to put 100s of rounds through. Even the barrel need not be much more than a piece of pipe. It's basically a high tech zip gun. Chamber and other dimensions can be found here:
https://saami.org/technical-information/cartridge-chamber-drawings/All the info is out there to make something that will work.
But the shooter should have kept in mind (if they wanted to get away) that all of this effort would be to construct something disposable, one use and done, to be destroyed as soon as it was 'safe' to do so.
Unless....
Consider the apparent reason for the killing of this CEO is not just reprisal, but is to send a 'message' to other CEOs.
With the Left's reaction, this is an act of violence intended to change the behaviour of a group of people out of fear, the very definition of a terrorist act.
Regardless of motive, or the other facts of the case, with manifesto and writing on cartridge cases, that appears to be the case. So not so simple as murder, and he failed to destroy the evidence.
Which makes little sense, except in the case he wanted no one to know beforehand (so he could ambush hunt the CEO unopposed by security), and didn't care afterwards because the 'message' had been sent.
There is no 'message' if he isn't caught, if the manifesto (or whatever it is) does not get out. It's just a random appearing shooting.