No Criminal Inference
It is not possible to conclude that a crime was committed just because someone discharged a firearm in self-defense. We need look no further than Gaige Grossgkreutz. He claimed to be observing the protests as a legal observer for the ACLU. He heard shots fired and saw a commotion and ran over to Kyle Rittenhouse. He testified that he believed Kyle Rittenhouse was an active shooter (clearly a correct assessment after the fact). He tried to subdue Rittenhouse, in case Rittenhouse had, in fact, committed a criminal act, and to deter further criminal use of his long gun. To this end, he says he pointed his Glock at Rittenhouse (though he also says it was "unintentional"). What he didn't do is pull the trigger.
However, Kyle had already pointed his rifle at Gaige before he drew his handgun, and he testified that he thought he "was going to die". Therefore, if Gaige had pulled the trigger, then he would apparently have had the exact same defense as Kyle. He didn't, because:
“That’s not the kind of person that I am. That’s not why I was out there,” he said. “It’s not who I am. And definitely not somebody I would want to become.”
On the other hand, Gaige had every reason to believe that Kyle was going to shoot him, because he saw Kyle re-rack his rifle while it was pointed at him. Gaige would have had an open-and-shut self-defense case if he had fired first, given the outcome of Kyle's trial.
No Criminal Charges
Most importantly, it should be noted that up to this moment, Gaige Grosskreutz has not been charged with any crimes relating to the Kyle Rittenhouse slayings, despite Kyle shooting him "in self-defense". This should be the clearest evidence yet that the victim of a self-defense shooting need not be a criminal. In a very unusual outcome, it could have been the case that both Kyle and Gaige shot each other. If they had both survived, they could have both claimed self-defense. And presumably, they could both possibly win on their claims, proving that the "aggressor" in a self-defense case need not be engaging in criminal activity to justify a self-defense argument.