Mr. Chang's side used a smoke bomb, clearly signaling an intention to retreat from this battle. The three individuals with distinct characteristics of District 002 were all locals, which was why Brother Lei had issued a threat.
Should they wish to hide in the game, nobody could stop them now. And with a bomb on the speeding train, backup Players couldn't arrive in time; the goal was to give the opposition some apprehension.
Once the tunnel exploded, the deaths wouldn't be limited to just a few people.
Of course, Brother Lei's side had casualties and it was hard to swallow this grievance. The best outcome would be to resolve these individuals on the train!