Gil is unlikely. He does have a big gun like that, but when we last saw him he was on Castle Wulfenbach captured by Klaus. Even if he somehow escaped, He couldn't have arrived there in such a short time. Remember, Tarvek landed using the Falling Machine, and I don't think Gil has another one. So if he escapes, he has to use an airship which is much slower than that, and probably can't land easily in the middle of the town.