In fact If people are taking arms against each other it is combat.
In fact it was the criminal who chose to be a criminal, to arm himself against police, to conceal himself, and to do the opposite of what people (police in fact) aiming guns at him instructed him to do.
There is no way to tell that he did not have a gun.
There is no way to know if he could, or would, inflict a mortal wound, and what little doubt there could be (none in this case) he lost the benefit of a long time ago.
These police officers risked their life to save the life of a scumbag. When they did not shoot him where he crouched, they risked their lives and gave him a chance to save their own. When they told him to drop his weapon, they gave him a chance to save his life by risking his own. When he stood up and did not get mag dumped, they risked their lives to give him a chance to save his own. When they tazed him instead of shooting, they risked their lives to give the criminal a chance to save their own. When he lunged at them with a knife their considerable patience had ran dry.
Nothing of value was lost, luckily. But the actual god honest truths is that those police officers need to have their procedure seriously reviewed, because they took needless risks which could have resulted in an officer being injured or killed. Personally i would not fault the officer for shooting him in the head the instant he saw him crouching with a knife in the closet, as that alone far surpasses the threshold for necessitating an instantaneously deadly response.
But by the time he stood up with a knife, he should have been eating lead. That is far, far beyond a "reasonable risk" for any officer to take. Any number of factors can contribute to a motivated assailant continuing to advance and stab at full speed even with many gunshot wounds. They got lucky, that either their shots landed right, or that he just laid down. Police could have VERY easily died that night.
And for fucking what.