Tyler is right. This is no shutter or mirror problem. If you set a shutter speed faster than the flash-sync speed then you'd get a dark "band" but it would be a rectangular section that was too dark -- not these odd shaped shadows as seen here. Same would be true if the mirror were sticking.
My suspicion is that:
1) something is blocking the flash (that should be easy to spot)
2) something really was blocking the lens... the lens-strap, a finger, something
3) something is inside the camera sensor housing. But something in the camera would be very easy to spot. Just remove the lens and put the camera into manual sensor-cleaning mode. The mirror will swing up and the curtain shutter will slide open. If something large enough to cause that shadow is in there, you're going to see it.
4) something is inside the lens (very unlikely). If you think there's something loose inside the lens, just remove the lens from the camera and look through it with the front and rear caps removed. Canon lenses always park the aperture blades in the retracted position so it's really easy to see through them.