Stark, Florida (AP) - An Army combat veteran whose Gulf War experience has caused serious mental problems is scheduled to be executed in Florida on Thursday after his girlfriend and her three young children were shotgun killing.

Unless there is a last-minute probation, Jeffrey Hutchinson will begin a fatal injection at 6 p.m. Thursday at Florida prison near Stark. If executed, it will be a death arrest warrant signed by Gov. Ron DeSantis, which will be the fourth in Florida this year, with a fifth execution scheduled for May 15.

Hutchinson, 62, has long claimed he was innocent and two unknown attackers were to kill people, part of a U.S. government plot to silence him about his claims on the disease of the Gulf War and other issues affecting veterans. Hutchinson served in the military for eight years, part of which was an elite ranger.

However, court records show Hutchinson argued with his girlfriend, Renee Flaherty, 32, in the murder case in Crestview, Florida, and then packed the clothes and guns into trucks. Hutchinson went to the bar for some beer and told staff member Flaherty was angry with him before he suddenly left.

Shortly after a male called Hutchinson's 911 operator, "I just shot my family," Flaherty shared with three children: Geoffrey, 9, Amanda, 7, and Logan, 4. All of this was killed by a 12-port shotgun found on the kitchen counter. Hutchinson was placed in the garage by police, his cell phone was still connected to the 911 center and was shot wound on his hand.

At the 2001 trial, Hutchinson's defense was based on a claim that two unknown men came to the house and killed Flaherty and the children after struggling with them. A jury found Hutchinson guilty of four counts of first-degree murder and was sentenced to life imprisonment for Freherty's killing and three death sentences on the children.

Since then, Hutchinson has filed many failed appeals, many focusing on mental health issues related to his military service. In late April, his lawyer tried to delay his execution date by claiming Hutchinson was insane and therefore could not be executed.

Bradford County Circuit Judge James Colaw rejected the argument.

"The court found that Jeffrey Hutchinson does not have any mental illness at present," Colaw said in an April 27 order. “The court held that Mr Hutchinson’s alleged delusion was clearly wrong.

Hutchinson's lawyer said in court documents that he suffered from the Gulf War disease, a series of health problems caused by the Iraq War of 1990-1991 - as well as post-traumatic stress disorder and paranoidness and paranoia related to his claims that he was a target of government surveillance.

One of his attorneys, Chelsea Shirley, said Hutchinson "decades of delusions were to keep his efforts silent. The two experts concluded that he was not capable of executing the execution. Based on these facts, we think the court believes that Mr. Hutchinson has the ability to be executed, but we are not surprised."

According to the state Department of Corrections, Florida's deadly injection regimen uses sedatives, paralysis and a drug that blocks the heart.

So far this year, 14 people in the U.S. have been executed in Florida, including Hutchinson as fourth. Glen Rogers is scheduled for the fifth execution in Florida on May 15, and Glen Rogers was convicted in 1997 for killing a woman in a motel. Rogers was also convicted of murder for another woman in California and was believed by investigators to kill others across the country.