Location: Chapter 2
After killing the first three enemies in the 2nd chapter you will come to some sort of bar. In the center of the room is a mounted machine gun. It is surrounded by a circular table. Kill all of the enemies except for the machine gunner. Cover behind the circular table and vault over it when the Circle (PS3) / B (X360) Button is displayed. It's recommended to play on the easiest difficulty. The machine gun will probably kill you otherwise.