Use the tools and shoot, there are three kinds of bullets, the candy bullet will add one charge, the live bullet will minus one charge, the blank bullet do nothing.

The tools can only tell the possibilities. By magnifier, you can know which kind of bullet this one is not. By phone, you can  know which kind of bullet a random one is not. By switch, you can transfer kind of bullet of this one, but not sure to which kind. When charge of alien comes to zero, you can win the game.