An Oklahoma inmate who was convicted of the 1986 murder of his fiancee was executed Tuesday evening despite claims that he was insane and ineligible for the death penalty.

Garry Thomas Allen, 56, was given a lethal injection at the state penitentiary in McAlester for fatally shooting 24-year-old Lawanna Gail Titsworth, outside an Oklahoma City day care. Allen was declared dead at 6:10 p.m., according to Jerry Massie, spokesman for the Oklahoma Department of Corrections.

Titsworth had moved out of the home she shared with Allen and their two sons four days before her death. Allen confronted Titsworth outside the day care and shot her twice in the chest. She ran with a center employee toward the building, but Allen pushed the worker away, shoved Titsworth down some steps and shot her twice more in the back, according to court records.

A police officer responding to a 911 call tussled with Allen before shooting him in the face, according to court documents. Allen was hospitalized for about two months with injuries to his face, left eye and brain.

Allen entered a blind guilty plea to first-degree murder, meaning he had not reached a plea deal with prosecutors and did not know what the sentence would be. A judge sentenced him to die.

Allen's attorneys argued he was not competent enough to enter the plea. They also contended he was mentally impaired when he killed Titsworth, that he had been self-medicating for a mental illness and that his mental condition became worse on death row. The U.S. Constitution forbids the execution of inmates who are insane or mentally incompetent.

A judge halted Allen's original May 19, 2005, execution after a psychological examination at the prison indicated Allen had mental problems. Three years later, a jury rejected Allen's claims he should not be put to death.

The Oklahoma Pardon and Parole Board had voted in April 2005 to recommend that Allen's death sentence be commuted to life without parole. That clemency recommendation wasn't acted on until this year, when Republican Gov. Mary Fallin denied it.