Why did Brother Hua get more flies?

Brother Hua gave the fly a few more injections to ease his brother's pain. According to relevant public information, "Tears Running" is a Hong Kong film. The ending of the film is that a fly was shot and killed by the police while stabbing a witness. In order to reduce his brother's pain, Brother Hua stepped forward to make up the gun for the fly and was also shot and killed on the street by the police on the spot.