If it doesn’t have a name, it’s just called the Gunfire Movie Interlude. It was created by Chung Chi Wing for the film. Strictly speaking, it cannot be said to be an original episode of Gunfire. This song was used in another Hong Kong film in 1998, called "20 Years of Murder", and the author was also Chung Chi Wing. Because that movie is not as famous as Gunfire, nor is it as good at using Gunfire, so people only know it as an episode of Gunfire.

But this piece of music really matches "Gunfire"