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FORT WORTH -- Friday, the man at the center of a 2011 car pileup and murder investigation took he stand in his own defense.

Thomas Lester Harper is accused of shooting and killing 18-year-old Clarence Robinson, who police say was rushing to Harper's aid after Harper caused a car accident involving multiple vehicles. Police say as Robinson attempted to help one of Harper's children in the 2011 Arlington crash, Harper pulled out a gun and shot Robinson.

In the murder trial in Fort Worth, the 30-year-old defendant said he was exhausted the day of the alleged crime because he hadn't slept the night before. He said he drank an energy drink before taking his twin toddlers on a drive. While driving, Harper said he was having a heated discussion with someone on his cell phone.

At some point, the massive car accident happened on Collins, and Harper told the jury he was dazed and not sure what was really going on. But he did remember asking people not to help him or his children at the scene.

He said he panicked, and when a young Good Samaritan tried to help, he grabbed a weapon from his car.

'I fired the weapon,' he told he jury. 'I felt like my kids were in danger.'

The trial resumes Monday.

E-mail lzakalik@wfaa.com

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