The important part is bolded.
I do wonder though if you wouldn't get shot for your troubles. Cop's taking a beating, all of a sudden gunfire erupts; do you know that you're being rescued or under further attack? Do you have the situation awareness and self control to determine that? Stepping in to help is risky. Either way, glad it all turned out well.
That'd be my main concern. Not even from the officer under attack but from another unit arriving on scene. To many now just shoot first and sort it later.