A twice-convicted killer with a history of violence that continued even after he was sent to death row was headed for execution Tuesday for gunning down two video store workers during a robbery 14 years ago in Dallas.

Leon David Dorsey IV, 32, would be the seventh prisoner executed this year in the nation's most active death penalty state and the first of two inmates scheduled to die this week. Two more are to die next week.

The U.S. Supreme Court earlier this year upheld his conviction and death sentence and no late appeals were filed to try to block Dorsey's lethal injection.

Prison records showed that since Dorsey arrived on death row eight years ago, he's had at least 95 disciplinary cases, including a 2004 attack where he used an 8 1/2-inch shank to stab an officer 14 times in the back. The officer's body armor prevented serious injuries.

Less than two weeks ago, authorities recovered another shank from his cell. His threats of violence kept prison officials from making him available for media interviews as his execution date approached and his frequent disciplinary issues kept him in a prison system classification reserved for the most troublesome inmates.

"He's mean," Toby Shook, a former Dallas County assistant district attorney who prosecuted Dorsey for capital murder, said, calling him a "true psychopath."

"Wherever he's been he's done stuff like that," Shook said. "He's very smart, very organized. ... He just was always headed in this direction. Every day he was looking to hurt someone. It was the only satisfaction he got in life."

Dorsey already was in prison, serving 60 years after pleading guilty to killing a woman during a convenience store robbery, when a Dallas police cold case squad gathered enough evidence to tie him to the unsolved shooting deaths four years earlier of James Armstrong, 26, and Brad Lindsey, 20, at a Blockbuster Video store in East Dallas where they worked.

Evidence showed Dorsey, who called himself "Pistol Pete," cased the place on Easter Sunday night in 1994, then returned after midnight to steal $392 from a cash register. He shot the workers when Armstrong had difficulty opening a safe at gunpoint and Lindsey tried to run.

Most of the crime was recorded on security cameras in the store.

Dorsey initially was questioned about the slayings after his girlfriend reported to police that he had admitted the shootings to her. But police initially believed the 18-year-old was too tall, based on images from the security tape.

"Leon is a fairly tall fellow," said his trial attorney, Doug Parks. "The question is whether he was too tall to be the person in that video. That basically was the defense. The physical evidence showed it was not him regardless of what he said."

When the case was reopened in 1998, Dallas authorities had the tape analyzed by the FBI and determined Dorsey could have been the gunman.

"He got away with it a long time because technology hadn't caught up to him," Jason January, who prosecuted the case with Shook, said.

Five months after the video store killings, Dorsey killed a 51-year-old Korean woman, Hyon Suk Chon, at the convenience store she managed in Ennis, south of Dallas. He was in prison for that slaying when he was questioned again about the double slaying and confessed.

"You hate to see that, knowing that potentially if the technology had been as good when the crime was committed, someone else would not have been killed," January said.

Dorsey also admitted the murders to a reporter in an interview from prison while he was awaiting trial.

"I've done cut folks; I've done stabbed folks; I've killed folks," he told The Dallas Morning News. "But it don't bother me."

The interview was among evidence prosecutors used to convince a jury he would be a continuing threat, one of the criteria for the death penalty in Texas.

Dorsey at age 12 moved to Waxahachie to live with his grandparents after he was booted from Germany where his mother was stationed in the Air Force. Records show when he was 14 he took a gun to school and fired it. At 16, he fired at a couple driving in a car.

"He'd walk down the street with a sawed-off shotgun tied to his arm and with a coat on and then just throw it open — just to see the reaction of people," Shook said. "He's a piece of work."

On Thursday, Michael Rodriguez, one of the infamous "Texas 7" prison escapees, has volunteered for execution for his part in the fatal shooting of a Dallas-area police officer, Aubrey Hawkins, during a robbery while he and the six other escapees were fugitives in December 2000.