After you beat the Tank, and go into the Nuclear Storage Facility, go up the ramp to your left. At the top of the ramp, take a photo of the glass infront of you. Don't zoom in after you get to the top of the ramp, just take a pic. When you look at the photo later on in the Photo Viewe, it will contain a ghost, holding a knife, wearing a spiffy Gumbi shirt.