An American man convicted of killing his girlfriend, her mother and a man he claimed owed him $US2000 (A$3000) was put to death in a record 11th execution this year by the state of Florida.

Windom’s face was obscured by a sheet when the curtain was raised to the execution chamber shortly before a three-drug injection was administered. In his final moments, Windom said something about being on death row but it was not intelligible. Then, as the drugs began flowing, Windom started to take deep breaths. His legs twitched several times, and then he was still.

Windom was the 30th person executed in the US to date in 2025, with Florida leading the way behind a flurry of death warrants signed by Republican Governor Ron DeSantis. A 12th inmate, David Joseph Pittman, 63, is scheduled to be put to death in the state on September 17.

Court records show a friend told Windom the day of the killings that Lee — who supposedly owed Windom $US2000 — had won $US114 (A$174) at a greyhound racetrack. Windom told the friend that “you’re gonna read about me” and that he planned to kill Lee.

Windom went to a Walmart to buy a .38-calibre revolver and a box of 50 shells, according to court testimony. Not long after, Windom drove to find Lee, located him and shot him twice in the back from his car, followed by two more shots standing over the nab at close range.

Then Windom headed to Davis’ apartment and fatally shot his girlfriend “with no provocation” in front of a friend, court records show. Windom randomly shot and wounded another man before encountering Davis’ mother, Mary Lubin, as she drove to her daughter’s apartment. Lubin was shot twice in her car at a stop sign.

Windom received death sentences for the murders and a 22-year sentence for the attempted murder. Davis was the mother of one of Windom’s children, a daughter who had sought to block the execution from being carried out.

“Forgiveness comes with time, and 33 years is a long time. I, myself, have forgiven my father,” his daughter, Curtisia Windom, said in a statement from an anti-death penalty group that delivered more than 5000 petition signatures to the governor this week, urging him to intervene.

The inmate’s lawyers had filed numerous appeals over the years, including a claim that evidence of his mental problems should have been introduced at trial. But the Florida Supreme Court ruled that was not prejudicial against Windom because prosecutors then would have presented evidence that he was a drug dealer and the two women he killed were police informants.

Many of Windom’s appeals had focused on claims that he was represented by an incompetent lawyer when it came to presenting mental health evidence.

His final appeal was rejected on Wednesday by the US Supreme Court.

Since the 1976 restoration of the death penalty in the US by the Supreme Court, the highest previous annual total of Florida executions was eight in 2014. Florida has executed more people than any other state this year, while Texas and South Carolina are tied for second place with four each.

Before Thursday, the last execution in Florida took place on August 19 when Kayle Bates, 67, received a lethal injection for killing a woman he abducted from an insurance office.

Florida executions are carried out via a three-drug injection — a sedative, a paralytic and a drug that stops the heart, according to the state Department of Corrections.