This happened in public, so there should be a lot of witnesses to evaluate the “self-defense” claim. From what we know about the victim, he does not sound like someone who would get violent over a misunderstanding about where someone was supposed to be sitting, and him being violent would be the only rationale for him being fatally stabbed.
You cannot use a weapon in a physical altercation. All the blaqq kid had to do was move. He went there to cause a problem, why else carry a weapon? To me it seems to be an open and shut case of premeditated first degree murder. Hang him high.