Get into the Schafter and drive to the Dragon Heart Plaza. Tony will give you an Assault SMG, which Luis will call "some sci-fi shit". When you finally arrive at the meeting, you'll see a Chinese mobster speaking with a familiar character. After Luis is rather clear that he and Tony aren't patsies to sort out the Chinese character's licensing issue, a gun is drawn. Seemingly in a bind, Luis eventually overpowers the Chinese mobster, kicking the gun out of his hand and sending him into an unconscious swoon on the concrete ground. Unfortunately, a bullet is fired off from the gun, and the noise from the shot has alerted his friends.
You have to escape the building, using the P90 to kill all opposing Triads as you descend. Some enemies will have grenades, so be careful in the narrow hallways. There is a Combat Shotgun in one of the unfinished rooms, and some armor in another. Once you reach the bottom, drop Tony back at his house to complete the mission.