While chasing the man, go behind the satellite dish then jump onto the ledge. Go onto the fire escape. Make sure you do not fall. Try jumping on the fence or the side of it without losing a life, then jump down. You will see a door. Enter to find molotov cocktails, grenades, and ammunition. Then, get out of the other door and you will end up under the staircase where the men who were shooting at you on the roof are located. You can kill them quickly.