Bottom line, this was justified self defense. Sometimes when you fear for your life and safety and you protect yourself and others the perp is injured or killed. The perp could have avoided this by not threatening others.
NYC has the opposite of a "Stand Your Ground" law. The principle there is you're not allowed to defend yourself until you have exhausted all options for retreat. In NYC, actively intervening in the defense of a third party when you yourself are not under direct threat is a crap shoot.
And it wasn't a "choke hold." A sleeper hold -- properly administered -- doesn't compromise the airway. No compromised airway, no choking. Those of you who persist in parroting the "choke hold" myth are contributing to the prosecution's case.
The principle effect of a sleeper hold is to constrict the jugular veins. The carotid arteries don't get the same constriction because they're located deeper in the neck than the jugulars and the arteries themselves are more resistant to compression. The jugular will collapse under 4.5 lbs of pressure but the carotids take 7-11 lbs.
Compressing the jugulars restricts the flow of blood leaving the brain. And if the carotids are less compromised (which in general they will be), the compressed jugulars will cause a spike in blood pressure within the cranial vault.
A baroreceptor called the carotid sinus senses the high blood pressure and sends a signal to the heart so slow down. When the heart slows, blood pressure drops precipitously, triggering a condition called reflex syncope.
And straight from Wikipedia, "Reflex syncope is a brief loss of consciousness due to a neurologically induced drop in blood pressure and/or a decrease in heart rate."
https://en.wikipedia.org/wiki/Baroreceptor
https://en.wikipedia.org/wiki/Reflex_syncope