A former St. Louis police officer Thomas Carroll, 52, pleaded guilty on Wednesday to beating a handcuffed suspect. He acknowledged that he had thrown the suspect, Michael Waller against the wall and punched him in the torso. He denied the accusation that he had stuck a gun in Waller’s mouth to threaten him.

Waller was arrested in July 2014 and found to have a credit card on him belonging to the daughter of Officer Carroll. Police officers located Carroll to let him know about the credit card and where to find Waller.

The officers who assisted Carroll have not yet been identified.

Assistant prosecutor Bliss Worrell pleaded guilty in October of helping to cover up the case. She admitted to filing charges claiming that Waller had been resisting arrest in order to hide Carroll’s assault on him while in handcuffs.

Carroll told Worrell and others in a conference call that he had thrown Waller against a wall, beat him, threw a chair at him and shoved his “pistol down the guy’s throat,” Worrell’s plea says.

If Carroll’s denial of using the pistol to threaten Waller is proven to be a lie at the sentencing trial, it could substantially influence the length of his sentence.

In his guilty plea, Carroll admitted to approaching Waller as he was seated in another officer’s patrol car. He yelled that the man had made “a huge mistake” and “broke into the wrong girl’s car.”

After Waller had been taken to Central Patrol police station, Carroll’s supervisor told him to stay away from Waller, yet Carroll entered the interview anyway and assaulted Waller while he was shackled to the floor.

Carroll faces a $250,000 fine and up to 10 years in prison for his guilty plea to one count of “Deprivation of Rights.”

“I have zero tolerance for the actions of police officers who discard justice for their own angry vendetta,” said U.S. Attorney Tammy Dickinson. “I know the vast majority of law enforcement officers join me in repudiating this brand of brutality. This former police officer not only violated the civil rights of a person in police custody, he violated the public trust and his oath of office.”