Not saying it happened here, cause it didn't: you can render someone unconscious or dead with pressure to the neck around carotid arteries. This restricts oxygenated blood from reaching the brain. Sometimes fighters distinguish between a blood choke and the more obvious choke pressing on the front of the neck. Plenty of info online. Plenty of police departments succumbed to political pressure from ignorant virtue signalers and banned any restraint of the neck.