Edit: I got a better look at the surveillance video. Looks like what is actually happening is that the guy's gun is under-gassed. The rounds aren't producing enough energy to fully cycle the weapon, resulting in jams or requiring him to manually chamber the next round. There goes the professional international assassin theory, I'd think a professional would test their set up to make sure everything was adjusted to cycle properly.
The way these are set up - When you fire a normal semi-auto pistol the energy from the shot pushes the slide back so the gun can chamber a new round. You can then fire again immediately.
With these things the slide is locked closed when you fire. That means the slide doesn't move, which means it doesn't make noise. All the gas goes out the barrel through the suppressor. The brass stays in the chamber.
All of this combines, with the right silencer and ammo, to make a gun that is ridiculouslly bad action movie quiet. If you're standing right next to it you'll hear something but it's not going to sound like a gunshot.
Idk what the hell is going on here but it sure does look like some cool John Wick level shit.
not a gun guy, but I'm just gonna say that once I read a book where a guy used custom loaded 22s fired from a chambered down pistol so that there would be no chance at ballistics matching anything. the round would be too mangled. additionally, the loads were subsonic so his homemade suppressor would be even more difficult to recognize as a gunshot by anyone nearby. they would hear something for sure, but nobody would mentally register it as a gunshot.
this configuration resulted in a low power, close range single action that would require him to manually work the action after every round and make it easier to keep track of his brass.
he did all this because it was never going to be used in a real fire fight. he was only using it to cap unarmed people who were caught completely off guard.
when I saw the video, the first thing I thought of was this book I read like 20 years ago.