Yes.

Looking at the 5 basic rules of self-defense, things aren't obvious

Innocence -- was he doing something against the law? Was he picking the fight? We don't actually know though the gun firing at almost the exact time the pepper spray does means he was already brandishing his gun. That alone is enough to prosecute.

Imminence -- was a threat on his life about to happen? At best he can claim he feared the guy would take his gun, but that's also murky given that it's a crowd of people and he should have a bunch of friendly people around him given that he's a security guard who's supposed to be with a TV crew.

Proportional -- was his lethal response proportional to the non-lethal threat present?

Avoidance -- there is no duty to retreat in Colorado as I understand it (though I believe it can still be mentioned by the prosecutor that he could have just walked away).

Reasonableness -- would a reasonable person (in this case, a jury member) feel pepper spray at a protest was good enough reason to kill someone?

I'm not going to say with certainty that it is or is not self defense, but a jury and interviews with everyone nearby absolutely needed to happen here.

This prosecutor apparently didn't even bother with the sham that is a grand jury which makes the situation look even more political (obvious self-defense like Rittenhouse is prosecuted while this murky case is not). That kind of perception (whether true or not) absolutely MUST be avoided.