Eight years ago, Navy SEAL Chris Kyle was murdered.

He was shot and killed alongside his buddy Chad Littlefield by Eddie Ray Routh, a former Marine with serious mental problems. The three had gone to a range to shoot some targets near Glen Rose, Somervell County, Texas, to unwind and help Routh battle his demons.

Chris Kyle was arguably the best sniper in U.S. military history.

On the day he died, Kyle secretly texted Littlefield, sitting next to him in the pickup, saying Routh was “straight-up nuts.” Kyle’s wife, Taya, “could tell something was up” that afternoon when she spoke to her husband. Kyle sounded “irritated,” as she testified in court. Then he never responded to a text asking if he was OK.

Littlefield texted back: “He’s right behind me, watch my six,” telling Kyle in military slang to watch his back.

The last time Taya Kyle spoke with her husband, she testified at the trial, was around 3 p.m. She reached him on his cellphone, and he told her they had just arrived at the lodge. But their short conversation left her fretful.

Members of the military with the coffin of Chris Kyle at Cowboys Stadium in Arlington, Tex. (Larry W. Smith/European Pressphoto Agency)

Arriving at the range, they carried several rifles, five handguns and boxes of ammunition, and protective earplugs to an open platform, 12 feet wide and sheltered under a corrugated metal roof. Kyle and Littlefield were carrying loaded .45 caliber 1911-style pistols on web holster belts. They began using the range, and investigators determined that a .38 single-action handgun was fired downrange, as was a Colt .45 cowboy-style revolver.

Routh later said that it bothered him that Chad Littlefield was not shooting; it somehow made him a threat. At some point, Routh armed himself with a 9mm Sig Sauer P226 MK25 pistol — the model used by Navy SEALs — and a Springfield .45 pistol.