That caliber would have blown his head off and the bang would've been much louder. The suspect is a patsy imho and all aspects of the assassination are still to be investigated and many questions are to be asked. Why e.g. do you think it would be necessary to pave the crime scene a couple of days after the incident? Doesn't that smell to you like evidence has been destroyed?
What would be hidden by concrete? Seriously. This sounds like BlueAnon shit.
I have no idea what might have been hidden there or not. But since the official theory about the shot would have blown his head off, a plausible explanation is still to be discovered and to pave the crimescene new isn't helping the investigation to say the least. Why would it be necessary to pave a crime scene like that days after the incident?