'American Sniper' Suspect Tied to Chair on Suicide Watch After Being Tasered

Eddie Ray Routh has been charged with the killing of Chris Kyle. (Erath County Sheriff's Office)

The former Marine accused of killing Chris Kyle, America's most successful military sniper, has been placed on suicide watch and was Tasered after becoming aggressive and attempting to attack guards at the central Texas jail where he is being held, authorities said.

Eddie Ray Routh, 25, is accused of shooting Kyle, 38, a Navy SEAL who served four tours of duty in Iraq and authored the best-selling memoir "American Sniper," as well as another veteran, Chad Littlefield, 35, when the three men were at a rural gun range in Erath County, Texas, on Saturday.

Guards at the Erath County Jail used a Taser on Routh on Sunday night, after he became belligerent and refused to give jailers the tray on which he had been served dinner, authorities said.

Erath County Sheriff's Office

Eddie Ray Routh has been charged with the... View Full Size

Erath County Sheriff's Office

Eddie Ray Routh has been charged with the killing of Chris Kyle.

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When guards came to collect his tray, Routh "was trying to attack them," said Erath County Sheriff Tommy Bryant at a press conference.

An official at the county jail, unauthorized to speak for attribution, told ABCNews.com that Routh had been placed on suicide watch and was confined to a solitary cell in which he was tied to a chair using restraints.

Routh was arrested Saturday, after the men's bodies were found. Police chased down Routh, who was driving Kyle's stolen pickup truck, disabling the vehicle with tacks and arresting the suspect.

Police said Sunday that Kyle and Littlefield were both killed at close range using a semi-automatic pistol.

Routh was charged with two counts of capital murder and his bond was set for $3 million.

He offered no confession, or hint at a motive, police said.

Routh will be appointed an attorney, but will likely receive a lawyer experienced in handling capital cases.

Kyle founded FITCO, an organization that encouraged veterans to cope with post-traumatic stress through exercise. Police have not yet confirmed that Routh was diagnosed with PTSD.