FREEPORT, Texas -

The Freeport Police Department is conducting an internal affairs investigation after a videotape surfaced showing a former patrol officer slapping and tapping the head of a handcuffed inmate, police said.

Freeport police said the incident involving Sgt. Jay Newton happened about four years ago, but the tape just got out.

"I was mortified at what I saw," Police Chief Tyrone Morrow said.

Morrow said he wasn't the chief at the time of the incident, but he is now, so he's taking the matter seriously.

He said that he promoted Newton to lieutenant when he took the position over.

"The worst part was it was an individual that I had put my trust and confidence in," Morrow said.

Sources said Kristopher Stapleston was arrested on public intoxication charges, was handcuffed and waiting to be processed to be placed in a cell.

The video showed Stapleston and Newton, a supervisor at the time, exchanged heated words. The video then showed the 21-year-veteran of the force walk over and repeatedly tap Stapleston on the head before slapping him in front of the other officers.

"Totally unacceptable," Morrow said.

Sources told KPRC Local 2 that the tape only got out because the officer's soon-to-be ex-wife found it, made copies and ratted him out.

"Lt. Newton had obviously taken police evidence out of police custody and took it to his residence," Morrow said. "His wife got a hold of it and she attempted use it as a bargaining tool during the divorce."

Newton resigned before officials could launch their investigation.

The officers who witnessed the incident and did not report it also resigned before the investigation was launched.

The district attorney's office said Newton cannot face criminal charges because the two-year statute of limitations is up, but he's internally charged with tampering with police evidence, official oppression, assault and violation of standard of conduct.

KPRC Local 2 tried to reach Newton for comment, but no one answered the door at his home.

"Misconduct, no matter how slight, will not be tolerated under my watch," Morrow said.