That was after.
Grosskreutz thought Rittenhouse might be an active shooter and advanced on him gun drawn. He then decides not to fire, says he had hands raised (while admitting he pointed his gun at Rittenhouse during all this chaos).
The Prosecutor even asked him why he didn't shoot Rittenhouse first.
Unfortunately, there are people drawing the conclusion that his mistake was exactly that, not shooting first.
If he had shot first, it would have probably also been legitimate self defense under Wisconsin law.
Could of should of . You are playing in"' What if ? " .