So, I'm writing a story, and at one point this guy goes completely batshit insane at the guy that he believes killed his sister. The actual fight isn't clear - the POV describes it as a blur, after which he saw the 'killer' with blood pouring from his hairline, and had to practically strangle angry-brother to stop him from committing a murder. Angry-brother continues shouting/mouth-foaming at this guy until he suddenly seizes up and goes limp, revealing that he has passed out.
What I want to know is; is it possible for someone to become so consumed by misery, so overwhelmingly red-mist RAGE MODE that they lose consciousness? This guy has been keeping his grief and hatred bottled up and unseen, potentially for months. Does this seem believable to you, or do you think it's more likely that it happened because his air circulation was cut off by the fight-stopper guy's stranglehold on him? Or do you think he should just not pass out at all?
Angry-brother isn't known for being a hothead. He's usually quite calm and conserved. Your opinion?