According to Davis, the idea for the film came about after he saw a gun-battle scene from John Woo's critically acclaimed Hard Boiled in which Chow Yun-fat rescues newborn babies from gangsters. Desiring to make an action film centering on guns, he expanded the idea into a screenplay in 2000, accompanied by an animated footage with 17,000 drawings for the action scenes.
Davis got the inspiration for his film after seeing a scene from John Woo's "Hard Boiled" where Chow Yun-fat saves babies from gangsters.  He then expanded this idea into a screenplay in 2000, adding animated footage with 17,000 drawings to depict the action sequences.