A Long Way to Fall
Niko goes to meet Ray Boccino, an Italian mobster and friend of the McRearys. He wants someone who knows about their involvement in "waste management" to be wacked.
The target is Teddy Benavidez. He lives in Northern Algonquin projects. A ride to where he lives. Along the way, Ray will send you a text message to find someone named Alonzo, who knows which floor Teddy lives on. He is wearing a large jersey with 72 Ramierez on it. Intimidate him to find out where Teddy is (don't shoot him until after the yellow destination dot appears); after that, Alonzo tries to make a run for it. If you let him go, he calls Teddy and you are greeted by several armed men as soon as you arrive. If you kill him, you get the element of surprise.
The elevator is broken; it won't take you to the 20th floor, so you need to walk a few floors to his apartment. Teddy will have armed goons around corners and on the stairs (how they "greet" you will depend on what you do to Alonzo). Once you get to Teddy's apartment, look around and go into the kitchen (there's a first aid kit if you need it). On your way out of the kitchen, Teddy slams the door on Niko and heads for the roof. Fight your way to the roof and corner Teddy. Pull out your pistol, shoot him, and watch Teddy fall twenty stories to his death.