Not sure why everybody is suggesting a professional hitman based on the fact the murderer used a mask, gloves and a suitcase. I suppose you get that idea after watching an arbitrary crime movie. All it proves is intention.
The other clue is from the articles I've read is that there was no blood. No average person with a bone saw is going to be able to pull that off. Sorry.
A guy with a plan and a regular job?
didn’t take anything from the apartment either.
a regular joe who wanted to do this would’ve just shot him.
The fact that there were screams loud enough to concern neighbors could suggest it wasn't quite so professional. If it were a professional hitman, why not use something guaranteed to instantly and silently incapacitate him, first, then focus on cleaning up the evidence? Or did they try to, but it didn't go as planned?
One possible explanation would be that the goal was to send a message (to him before his death, and others after it), not to try to make him disappear without a trace. Though, either way, it doesn't necessarily mean it was a professional hitman.