Question about the plot to City on Fire (1987).

SPOILER


In the movie, Chow is undercover to bust a gang, but his superiors want him to wait until the big heist, in order to make a bigger bust. During the heist, the crooks get away and the police go after them. They shoot back at the police. But why does Chow participate in the shootout. Why didn't he just drop his cover and either arrest or shoot the crooks he was with?

Did he develop a bond with the main villain, enough that he is going to betray his entire police force?

Because it would make sense to keep up his cover in the middle of a firefight with multiple participants on the crooks' side - as soon as he tries to arrest one of them, the rest will turn on him and shoot him as well. I figure the plan is like Reservoir Dogs where the undercover cop has to wait until all the crooks are assembled at their post-heist rendezvous point where they can easily be surrounded by police.

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@Iroquois nailed it on the button, plus in some aspect Chow did have some sort of respectful bond with the gang leader, played by Danny Lee.So it was that "bond" that gave Chow a sense to show his loyalty while staying true to his job.

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But the crooks were shooting at the cops though, and they both had their backs turned to him while shooting at the cops. So wouldn't an undercover cop just shoot both of them when they have their backs turned, to prevent them from killing any more cops?

There were only two of them, and they had their backs facing to Chow, so Chow could have got them both. The cops then shoot one of them, and then there is only the one main villain left, and Chow could have gotten him, when his back was turned for sure.

Then I guess it is more a matter of him having conflicting loyalties per what WorldFilmGeek said. It is a heroic bloodshed film, after all.

Yep conflicting loyalties, would make more sense, it's just that they didn't seem to have much of a bond prior. They had a couple of bonding moments, such as throwing food on each other in front of the girls for for fun and the whole moment when he confides to him about his relationship problems. I guess that was enough though to have conflicting loyalties. I probably was thinking too much from the police side of it, rather than the bonding and conflicting loyalties side.

There is another thing about the movie I didn't quite understand. The main character, is having relationship problems with his gf yet he was hitting on his gf's friend, who is her roommate as well it seems, like when he flashed her and all. It seemed weird to me but were both women involved with him and his love interest, was just okay with her friend being involved with him too, or what was going on there?