Niko's cousin Roman is busy and wants Niko to pick up a friend of his, Little Jacob. Get any car and pick up Little Jacob, who is waiting near Outlook Park. After he has been picked up, drive to Schottler where Jacob is going to get revenge on some goons.
On the way, Jacob gives Niko a pistol to help him shoot down the goons. Go up to the lookout spot marked on the radar and bring out the pistol. Watch the cutscene as the goons close in on Little Jacob
Jacob begins to open fire on the goons, however, he wasn't expecting this many. That's your cue to open fire, as well. There are three enemies on the ground near Jacob, but one also comes out of a door on the roof nearby. Jacob will alert Niko of the final goon near the door. Shoot the goon and if you're lucky, he may topple over the building making for an amazing death scene.