I just saw this picture you posted after I had previously posted about the “professional assassin.”
Those are unfired cartridges. This jives with the shooter working the slide because he had a malfunction, at least twice. It doesn’t appear to be a Welrod either, the firearm slide skinnier than the silencer which denotes an attachment. I believe the entire barrel of the Welrod is one piece.
Why the need for a silencer when you are going to shoot somebody in front of people in a public place anyways?
The totality of all these circumstances doesn’t add up to a “pro” for me.
Again, this is just my 2 cents.
3 is either another unfired cartridge or an empty. Can't tell for sure because it's not facing bullet end toward the camera. However, it appears to be another unfired cartridge because there is no visible hammer dent on the primer. Again, gotta pick it up and look at it to be sure.
In one's humble opinion, this suggests an inexperienced shooter fumbling around with a weapon he's not experienced with. Previous posters have said he was using an oddball thing called a "Welrod", whatever that is... which requires each round to be manually cycled.
Question, is a "Welrod" something that someone in a blue city might acquire, to get around local restrictions on semiauto firearms? Why not just get a revolver instead?
Anyway my original opinion is changed. Not a professional job, like the famous (at least here in my locale) Roger Wheeler case in Tulsa OK back in the 80's where Telex executive Mr. Wheeler was unfortunately assassinated by a northeastern gangkster named Whitey Bulger in the parking lot at Southern Hills country club, using a Ruger Mark II .22 semiauto pistol fitted with a silencer. (Whitey was eventually caught and sent away forever despite his professionalism as an assassin.)
One could speculate about this guy's reasons, but his execution, as cold-blooded murders go, was kinda odd... but you know what they say, criminals tend to be stupid...