I was a volunteer fireman in a rural department for ten years. I frequently had a migraine the day after responding to a call -- my body's way of processing excess adrhenalin. It's a high-intensity environment, a contest played for higher stakes than any football game. The most dangerous thing I ever did was tackle brush fires with guys half my age. I'd end up exhausted on top of a hill, leaning on the fire rake, wondering where I'd get the energy to walk back DOWN that hill!
You're not dealing with construction workers at an accident scene, but with incredibly focused, energized, and passionate men. Not wise to interfere.
I've been in this exact situation and I managed to not get smacked by cops or firefighters. Just because your emotions are running a bit high, that's no excuse to flip out, just about run people down, and start fights at the scene. This guy is a complete moron.