It wasn't even a headshot too. The old ladder trick from the OG RE4 is back. If you climb the tower but do not move around and face the ladder, you can knife the ganados down safely without taking damage, until Salvador shows up. When he comes up, throw a flash grenade and make a run for it. This may not be the most exciting strategy, but it can save you a lot of resources. Only drawback is you won't get the loot I guess.