No one else saw the shooting of Kyle and his friend, Chad Littlefield, according to Upshaw.

CNN: STORY HIGHLIGHTS

Kyle and Chad Littlefield, the second victim, were found with multiple gun wounds and several guns at the scene.

BBC: Eddie Ray Routh undated police handout

An Iraq War veteran, Eddie Ray Routh, 25, has been charged in the killings of Kyle and his friend Chad Littlefield.

NPR: Procession Escorts Ex-Navy SEAL Kyle To Burial

Mr Kyle and his neighbour Chad Littlefield were reported to have been trying to help Mr Routh deal with post-traumatic stress disorder (PTSD).

BBC: Chris Kyle murder: War veteran Eddie Routh charged

Chad Littlefield, 35, was also shot to death.

CNN: Ex-Navy sniper killed at Texas gun range