Never bring a knife to a gunfight.
From the article it seems to me that the knife wielder came very close to winning this fight.
The victim’s 24-year-old cousin, who was waiting in his car nearby, overheard the noise and stepped out with his firearm, which he has a valid permit to carry. After he was also stabbed by the attacker (in the elbow), the cousin shot and killed the man.
The attacker managed to stab the cousin before being shot.
At close distances a knife can be as lethal as a firearm. An elbow wound sounds like a defensive wound. Perhaps he blocked a knife strike with his arm thereby receiving the elbow wound. Without video it can’t be said just how close the cousin came to losing the battle.
Lesson here; don’t let an attacker get close. Shoot him first.