Pete Souza's secret ?

Hello all,

I just received my Nikon d600 and have to admit I am a newbbie to photos.

That said, I am willing work to improve my skills...

I am a admirative of Pete Souza's photos and was wondering how to optain similar results if possible with a Nikon d600.

A typical example of nice photo but have no idea how he did that would be the following one:

http://lightbox.time.com/2012/10/08/pete-souza-portrait-of-a-presidency/#121

How does he do to have natural lights and shadows like that and relatively dark environment ?

Thanks in advance for your inputs.

rgds