(Reuters) - The state of Texas on Wednesday executed a man convicted of shooting a Houston police officer to death during a botched robbery of an adult book store in 1988, the state’s Criminal Justice Department said.

Robert Mitchell Jennings, 61, was pronounced dead by lethal injection at 6:33 p.m. CST at the state prison in Huntsville, the agency said in a statement. He became the first person put to death this year by Texas, which executed 13 inmates in 2018, more than any other state.

“To my friends and family it was a nice journey,” Jennings said in a final statement, according to the criminal justice agency. “To the family of the police officer, I hope this finds you peace, and be well and stay safe. Enjoy life’s moments because we never get them back.”

Jennings was condemned to die for the July 1988 slaying of 24-year-old Elston Howard, a vice officer in the city of Houston, during a failed robbery of an adult bookstore, according to state prison records.

At the time of the incident, Jennings was on parole after serving 10 years of a 30-year sentence for another robbery.

Howard was in the bookstore serving an arrest warrant on a clerk for showing movies without a license, the Houston Chronicle and prison records said.

Jennings shot Howard twice, and then shot him a third time after the officer collapsed on the floor, according to prison records.

A co-defendant, Robert Harvell, drove the getaway car. After Jennings got in the car and told Harvell that he shot a “security guard,” Harvell ordered him out. When Jennings refused, Harvell shot him in the hand, official records said.

Police later arrested Jennings at a hospital where he sought treatment for his wound. Harvell was arrested at his mother’s house and was later sentenced to 55 years in prison.

The Forgiveness Foundation, an anti-death penalty group, had urged the state to spare Jennings’ life, saying on its website that he “had no lasting, positive adult influence” as a boy who began using drugs at a young age and entered the juvenile justice system at age 10.

A federal appeals court earlier this week rejected a bid for a stay of execution that argued Jennings had lacked adequate legal representation for taking full advantage of possible appeals of his case.

A total of 25 people were executed in the United States last year, according to the nonprofit Death Penalty Information Center.