The sister of the former Marine accused of fatally shooting "American Sniper" author Chris Kyle and another man testified Wednesday that when her brother came to her home after the killings, he seemed "almost in a daze."

Laura Blevins, on the stand during the defense's first full day of testimony, said that when Eddie Ray Routh arrived, he told her he'd killed two people, The Dallas Morning News reported.

"He said he took their souls before they could take his. I asked him what he meant by that, and he said they were out to get him," Blevins said.

Routh, 27, is charged in the Feb. 2, 2013 deaths of the famed former Navy SEAL sniper and his friend Chad Littlefield at a shooting range. The trial has drawn intense interest, partly because of an Oscar-nominated film based on Kyle's memoir.

Routh has pleaded not guilty, and his attorneys are mounting an insanity defense. They say Routh was in a psychotic state at the time.

Blevins said that when she saw Kyle's truck, she began to fear he was telling the truth.

"When I was looking at him, he kind of looked like he was out of it, almost in a daze or something, and when I told him that I loved him, there was something in him that understood that," Blevins said.

Kyle had taken Routh on the outing after Routh's mother asked him to help her son, who family members have said suffered from post-traumatic stress disorder after serving in Iraq and in Haiti following a devastating 2010 earthquake.

Blevins testified that she'd distanced herself from her brother after he was hospitalized several times for mental health issues, fearing he could be a danger to her family.