Why did Bond point his gun at Mallory?

It just seemed odd to me. He points his gun at Mallory, doesn't shoot and just pauses for a moment, and then turns the gun to the fire extinguisher and shoots it. But why didn't he just go for the fire extinguisher first rather than pointing a gun at Mallory and risk getting shot by anyone who would think he was going to shoot Mallory?

Yeah, didn't make much sense but then neither did it make much sense for him to accuse Mallory of being a desk jockey when he knew very well that he wasn't and that M actually was.