There are pigeons on the roof of Randal's building. Get the bowl with corn from the Pub and the rat poison from of Matt's kitchen. Use the bowl with the pigeons to feed them for the first time. Then, go to the Pawn Shop and place the bowl on the gas cylinder to make popcorn. Return to the pigeons and feed them the popcorn. Add the rat poison to the popcorn. Feed the pigeons again and they will die.