A death row inmate and convicted cop killer was executed in Texas on Wednesday night, more than 30 years after he fatally shot a young Houston police officer.

The Houston Chronicle reports that Robert Mitchell Jennings was executed with a lethal injection on Wednesday at a prison in Hunstville.

In July 1988, Jennings shot and killed Officer Elston Howard during an armed robbery at a pornographic bookstore. According to the Houston Chronicle report, Officer Howard was writing a citation to the bookstore owner after an undercover operation found that the bookstore was illegally showing pornographic films when Jennings burst in. Jennings shot the officer twice in the neck, and then two more times after Howard had fallen. Jennings then robbed the bookstore and got into a getaway car driven by his friend, David Lee Harvell.

After Jennings told Harvell he thought he shot a security guard, Harvell insisted he get out of the car. When he refused, Harvell shot Jennings in the hand. Jennings took himself to a hospital for treatment, where he was subsequently arrested for the fatal shooting, and gave a written confession obtained by the Chronicle.

“I shot him in the back two times,” Jennings reportedly wrote. “After I shot him, the dude went to the ground between my legs, and he was still holding me by my legs, and I had to push him all the way down to the floor, and I then stepped over his body, and I went directly to the cash register.”

Over 100 hundred officers gathered outside the prison, some revving the engines of their motorcycles as Jennings was put to death. Houston Police Chief Art Acevedo spoke to reporters just ahead of the execution.

“The day is here,” Acevedo said. “The day of reckoning is here.”