Angel wants to follow the code of honor, and does not want to kill Marcelo outright. He doesn't want to lose his reputation with the Assassinos. We need to get the footage we found to Fumo, then we'll be able to kill Marcelo. Unfortunately, Fumo is hard to find, and he is hiding at a cemetery recently used for a Syndicate funeral. Of course! We need to head there to contact him.
Once you get close to him you'll discover that it is swarming with Syndicate gang members, as expected. You'll have to deal with all of them before you can get to Fumo. The cemetery is a very glitchy area, there aren't many good cover spots, so just keep moving, buying medkits, and killing Syndicate soldiers. Eventually you'll have cleared them all out and you can get to Fumo. Note that there is a medkit in the cemetery too, if you're running low.
After you have reached Fumo, you will need to escort him to his car. You will have lots more Syndicate to contend with, only now you have to protect yourself and Fumo. The waypoint can be a bit confusing as it shows Fumo rather than his car. Just stay near him and shoot any enemies that you see and he will lead you to it (it's a red pickup truck).
Once in the car, you need to drive Fumo back home. Having rescued him safely, Fumo will now be able to duplicate the surveillance tape and distribute it to the Assassinos. With that, you are in the clear to take down Marcelo, as Angel reveals to Fumo that he has, in fact, been Raul all along.
Reward: 10,000R$