Spoliers: Nice but strange

As a northern European coming from a completely different background, perhaps there is something I am not getting - and I respect that, should it be the case - but I found the whole "pranking thing" in the film's beginning to be quite strange. I especially found the culmination of it, with planting a tear gas booby-trap in someone's car, totally crazy.

Referring to my headline though, "Nice but strange", I expected the police officer who placed the tear gas to be consumed by guilt, but found it strange that he was not. In fact, that was the last we heard of the tear gas. As an audience though, I think that it was quite nice that we did not have to go through some slow-paced guilt sequences. Did anyone else react to that? Was it because the police office who died turned out to be a bad guy anyway and hence did not deserve any tears, a way to explain how an experienced, skilled police officer could be easily gunned down in the street?

Do not get me wrong though, I really enjoyed this film. I understand that 1980's Hong Kong culture in many ways can be quite different from today's nothern European, and I tend to overlook things I perceive as strange, but this one I just had to ask about!