"It's not an assumption, it's a fact," Harry said, "You don't know what you're dealing with and flailing you wand around is gonna add to the body count." And he didn't think that the count was that high, but he didn't want it to get any higher. And he didn't want it to be one of those faces he'd seen in this mess.
Harry was helping people though, whether the girl realized it or not. A skilled wizard in his own right, Harry was able to juggle out spells as needed and he even used some wandless magic, even if there was risk. Harry didn't like to use it too often because he knew how volatile it could be, but this was the sort of situation where he needed whatever he could use because Death Eaters were coming from all directions.
As Harry came around a corner, he saw a man who appeared to be lying down immobile. Harry cursed under his breath and took his eyes away from Keara, focusing instead on the man who had to be released from whatever curse or spell the Death Eaters cast on him.