For this mission you are informed that a leading member of the Assassinos, and a close aide to Andreas called Marcelo, has caught Venancio. This Venancio has long been an enemy of the Assassinos and in fact works for rival gang The Syndicate. He has been captured at the BoomDance Club, owned by Andreas. Head there to investigate further.
Once inside the club, you are told to enter the VIP section. You can see this upstairs, straight ahead, once you enter. Go up the steps to the right then walk into the waypoint.
Marcelo has Venancio waiting for you and it's up to you to do the honors. To shoot, you can either drag the camera around so that the center is on Venancio, then press the shoot icon on the right, or, tap Venancio and you will get a green reticule confirming you are locked onto him. Then press the shoot button to fire.
It turns out the guy we just killed was an imposter, and the real Venancio is making his escape as we speak. Another Assassino, called Fumo, has his eyes on the real Vanancio, so make your way to the beach to meet him. Follow the waypoints on your map.
Once you meet Fumo it becomes clear that Venancio is planning to run away, so you must give chase. It's up to you how you take him down, you can either align the camera behind him before firing, or tap on him to lock on, then fire. Take him out to complete the mission.
Reward: 250R$
Once you've done that, return to the yacht for your next mission.