Two long-form articles on the legend of Chris Kyle, both are good reads - the Schmidle article especially:

In the Crosshairs - Chris Kyle, a decorated sniper, tried to help a troubled veteran. The result was tragic, by Nicholas Schmidle. The New Yorker, 3 June 2013.

The Legend of Chris Kyle - The deadliest sniper in U.S. history performed near miracles on the battlefield. Then he had to come home, by Michael J. Mooney. D Magazine, April 2013.