@RnDanger @Lazarou @gabrielesvelto
I'm certified to teach advanced shooting courses including combat handgun shooting; here's my $0.02:
Being able to clear jams quickly is widely taught to shooters beyond beginners, such as peace officers.
The crime scene photo I saw showed a rejected round, with a damaged bullet (full metal jacket) still in its brass casing. To me that looked like factory ammunition.
I saw descriptions of words carved into the bullets and casings. I believe those could have caused the gun jams.
So, to me this doesn't suggest it was a professional hit so much as someone disgruntled and wanting to make a statement.