Eddie Ray Routh, the man found guilty of murdering Chris Kyle and Chad Littlefield in 2013, explained why he shot both men in a confession tape that was shown to jurors during the trial.

Kyle - a former Navy SEAL who came to global attention as the author of the bestselling autobiography American Sniper - along with his friend Littlefield, reportedly offered to take Routh to a shooting range.

After leaving the military, Kyle regularly worked with other veterans which led to Routh's mother reaching out to him and asking if he could help her son.

Routh had experienced post-traumatic stress disorder, and Kyle believed the visit to Rough Creek Ranch-Lodge-Resort in Erath County, Texas, would have therapeutic value.

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Routh, a 25-year-old Marine Corp veteran, explained his actions in killing Kyle and Littlefield during an interrogation with a Texas ranger, saying that he shot at Kyle first because he could 'clearly identify him'.

"I imagine they're headhunters, trying to hunt everybody down," he says in the clip, as quoted by CBS.

The audio from the footage was not released to media, but was played for the jury in 2015.

He continued: "If I did not take down his soul, he was going to take down mine."

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The ranger who interviewed Routh in the clip said in the courtroom: "He stated that he knew it was wrong to kill them, that he wished he hadn't done it, that if he could apologise to the families, he would."

Four months after the shooting, Routh told former Erath County Sheriff's Deputy Gene Cole: "I was just riding in the back seat of the truck, and nobody would talk to me.

"They were just taking me to the range, so I shot them.

"I feel bad about it, but they wouldn't talk to me. I'm sure they've forgiven me."

CBS This Morning

Routh's attorneys argued he was insane at the time of the murders, although witnesses for the prosecution stated they suspected he was faking schizophrenia.

On 24 February 2015, Routh was found guilty of the murders of both men.

Prosecutors decided before the trial not to pursue the death penalty, so the judge sentenced him to life in prison with no possibility of parole.

Littlefield's stepbrother, Jerry Richardson, resolved: "You took the lives of two heroes; men that tried to be a friend to you. You became an American disgrace."