A Texas man convicted of shooting and killing a Houston police officer in 1988 during a failed robbery at an adult bookstore was executed Wednesday, officials said.

The convict, Robert Jennings, 61, was pronounced dead at 6:33 p.m., 18 minutes after receiving a lethal injection and some 30 years after fatally shooting 24-year-old officer Elston Howard. In a final statement to his family and friends, Jennings said “it was a nice journey.”

Jennings, a convicted robber, was on parole for nearly two months when prosecutors say he entered Mr. Peeper's Bookstore with the intention of robbing the business. He had robbed the same store 12 days earlier.

FORMER VALET CHARGED IN BRUTAL MURDER OF WISCONSIN NURSE FOUND FROZEN UNDER VEHICLE IN PARKING GARAGE

Unbeknownst to Jennings, Officer Howard was in the process of arresting the store clerk on charges of operating a pornographic video arcade without a permit.

Jennings shot Howard twice in the head. The wounded officer staggered for a few feet before falling to the ground, where he was shot two more times by Jennings. The clerk later testified that the shooting was so quick, Howard never had a chance to unholster his gun.

Jennings was arrested hours later after going to a hospital to be treated for a gunshot wound – his accomplice shot him in the hand after becoming angry that Jennings had shot the officer.

Attorneys for Jennings had asked the U.S. Supreme Court to delay his execution, arguing that Jennings' trial attorneys failed to ask jurors to fully consider evidence — including details of his remorse for the officer's shooting and possible brain damage — that might have spared him a death sentence.

BANK HEIST HALTED AFTER WOULD-BE ROBBER GETS COLD FEET, RIPS UP NOTE

When he was arrested, Jennings confessed to the murder and told police he was remorseful about the killing, saying he would “face whatever punishment (he had) coming.”

Jennings received an execution stay in 2016. But the high court and lower appeals courts rejected his request to delay Wednesday's execution and the Texas Board of Pardons and Paroles turned down Jennings' request to commute his sentence.

CLICK HERE TO GET THE FOX NEWS APP

As a part of Jennings final statement, he shared his thoughts for Howard’s family.

“To the family of the police officer, I hope y'all find peace. Be well and be safe and try to enjoy life's moments, because we never get those back."

The Associated Press contributed to this report.