Elizabeta Torres wants you to oversee a deal that's going on. Packie McReary will give you all of the information that you need outside.
He tells you that there's a rifle on the roof of a building where you'll be able to watch over the exchange and make sure everything goes ok.
Drive a few blocks down and enter the building marked by your GPS. Go all of the way up the stairs to the roof. Once you get to the top, grab the sniper rifle, then go around the roof to the vantage point.
After a short cutscene, Packie and his associate will arrive. It's then your job to watch over the deal and make sure Packie is alright. You'll learn that crouching with a sniper rifle is better for your accuracy.
Pay attention to the on-screen instructions which guide you through how to use the sniper rifle.
Zoom right in on the enemies and wait until they kill Packie's associate. Once he's dead, take them all out. Go for headshots when they're not moving, but a shot to the chest will usually kill them too. Try to take them out quickly rather than waiting for the perfect shot. Also be careful of one of the enemies who will rush Packie and physically fight with him using a knife.
The last guy left alive will get into a truck at the end of the alleyway, so follow him closely and pop his head through the windscreen.
- There's plenty of ammo lying around after the bloodbath, so head downstairs and grab it all before it disappears.
- If you constantly fail this mission, you can get a nice stockpile of sniper rifle ammo. But why would you want to do that?
- There's a few pigeons on the roof to the right of the alley where the deal takes place, but I suggest you leave them and get them all at the same time with a guide.