This is such a simple case to figure out.
I've got a bad feeling this is Nutter maximum.
All the wounds were cause by shots fired from above an behind the victims.
OK...3 shots fired from the SN.
I can go for that.
Three spent shells were found at a location above and behind the victims.
OK, 3 shells found in the SN (I do wish Fritz hadn't manhandled them but...whatever)
Two bullets were recovered.
Oh dear...massively incorrect.
You were doing so well.
If you have a single scrap of evidence that CE399 was the bullet recovered from Parkland do share it.
Both the recovered bullets and all three shells were fired from a rifle found a short distance from the shells to the exclusion of all other weapons in the world.

How were the shells fired from a rifle to the exclusion of all other weapons in the world??

How stupid is that sentence.
PS: CE399 wasn't recovered from anywhere. It just magically showed up in the chain of custody when the FBI got involved.
The owner of the rifle left his fingerprints at the shooting location,
He worked there.
his palmprint on the barrel of the rifle,
clearly faked evidence
and fibers matching his shirt on the butt plate of the rifle.
Similar fibres
It doesn't take either Sherlock Holmes or Columbo to figure out who the assassin was. Even Inspector Clouseau could have cracked this case.
It's a pity at least 3 eye-witnesses described the shooter wearing clothes Oswald didn't own.
That one witness observed a distinctive "bald spot" that Oswald didn't have.
That this spot was only observable when the shooter was looking down the rifle, indicating a left-handed shooter, which Oswald was not.
That the only two witnesses to observe the rifle as it was being used didn't observe a scope.
That the shooter appeared to be a lot older than Oswald.
And lots and lots of other evidence pointing away from Oswald being the shooter.
Yeah, this is a slam dunk of a case.