HUNTSVILLE, Texas (AP) — Appeals appeared to be exhausted and no last-day legal attempts were expected for a man scheduled to die Tuesday evening for killing a father and infant son as part of a Christmas Eve 1987 rampage.

James Bigby, 61, would be the fourth Texas inmate executed this year and the sixth nationally.

Bigby was condemned for the fatal shooting of Michael Trekell, 26, and suffocation of Trekell's 4-month-old son, Jayson, at their home in Arlington. Evidence showed Bigby also was accused but not tried for killing two other men, believing they along with Trekell were conspiring against him in a workers' compensation case he filed against a former employer.

"I know I am guilty, and so do you," Bigby told police during a SWAT standoff at a Fort Worth motel before he was taken into custody.

His lawyer, John Stickels, said Monday nothing was in the courts to try to block Bigby's lethal injection.

"I don't necessarily agree with it, but it's his choice," Stickels said. "I don't want to give up, but certainly there aren't any issues to be pursued. I just don't like the state executing people."

The U.S. Supreme Court in 2015 refused to review Bigby's case after a lower federal appeals court had rejected arguments his trial lawyers were deficient, that instructions to his jury were improper and that evidence didn't support arguments from prosecutors that Bigby deserved to be executed because he was a danger to society.

At his 1991 capital murder trial in Fort Worth, Bigby grabbed a loaded gun from behind District Judge Don Leonard's bench during a court recess and barged into Leonard's chambers. The judge and a prosecutor wrestled Bigby to the floor and pulled the gun away and the judge continued presiding over the case.

Jurors were told about the attack, rejected Bigby's insanity defense and decided he should die. Then in 2005, a federal appeals court threw out his death sentence, saying the trial jury wasn't properly instructed to consider Bigby's paranoid schizophrenia as a mitigating factor when they were deliberating his punishment.

Three years later, another Tarrant County jury returned him to death row.

"I don't think anyone in the courtroom claimed he wasn't mentally ill, but there were too many dead people and a dead baby," Wes Ball, one of Bigby's defense lawyers at the new punishment trial, recalled Monday. "And going up and getting the judge's gun out of his drawer in court and going at him ... is kind of the icing-on-the-cake moment."

Bigby confessed to killing Trekell and the man's infant son. He was never tried for the killings of Calvin Crane Jr., 38, in nearby Fort Worth, and Frank Johnson, 33, in Arlington.

Court documents show Bigby, who had worked as an auto mechanic and had two previous prison stints for burglary, believed Trekell was conspiring against him in his workers' compensation lawsuit against a former employer, Frito Lay Inc., where he worked in a body shop.

In his statement to police he described how he shot Trekell with a shotgun while the man was at a kitchen table preparing steaks, then went to the infant's room and wrapped the child's head with cellophane he took from a refrigerator, suffocating him. Bigby then filled a bathroom sink with water and put the baby face-down into the water.

"I regret killing the baby but not the other," Bigby told police.

He said he went to the homes of Crane and Johnson, fatally shot each of them for what he believed to be their roles in the conspiracy against him in his workers' compensation case, and drove off in Crane's truck.