I downloaded the pic and opened it in Lightroom, then looked at the metadata info.

The info is as follows:

Copyright: 2013 The White House
Creator: The White House
Dimensions: 1024 x 683
Exposer: 1/320 sec at f / 4.0
Focal Length: 170 mm
ISO Speed Rating: ISO 400
Make: Canon
MOdel: Canon EOS 5D Mark III

I had my wife, who is a photographer and is fluent in both Lightroom and Photoshop, look at it, and she said this: NOT A FAKE...

It is a pretty clear pic, so I zoomed it in, and that is him shooting the gun.