A Harris County Sheriff's Office sergeant faces up to 50 years in federal prison after pleading guilty to five counts of attempted transfer of obscene material to minors.

John Fredrick Black, 46, entered the guilty plea in the Northern District of Florida, the U.S. Attorney's Office announced Tuesday, Sept. 29. Black had been employed by HCSO since 2003 and held the rank of sergeant when he was arrested in January. The Harris County Sheriff's Office patrols unincorporated areas around the Clear Lake communities.

The case began in January when detectives with the Leon County Sheriff's Office Human Exploitation and Trafficking Unit in Florida posed as a 13-year-old child in an online chat, FOX 26 Houston reported. Black continued communicating after being told he was speaking with a minor and sent obscene material of himself to the undercover detective, according to the Leon County Sheriff's Office.

The Leon County Sheriff's Office also found that Black had engaged in similar conversations with two other minors on the same platform. The agency said at the time that additional charges could be filed.

Black was arrested in Harris County on Jan. 26 on a warrant out of Florida. At his bond hearing, a Harris County judge set bail at $20,000 and ordered Black to surrender to Florida authorities immediately upon release.

"As soon as you get out, you go back to Florida … If I find any violations, I'm going to yank this bond in a moment's notice," the judge said at the January hearing, according to KHOU.

HCSO relieved Black of duty the day of his arrest. In a January statement, the agency said an internal affairs investigation was underway and that results would go before its Administrative Disciplinary Committee to determine further action, up to and including termination. No public update on that review has been released, and Black's current employment status has not been publicly confirmed.

Black pleaded not guilty to Florida state charges on March 4, WCTV reported. The federal case, prosecuted by U.S. Attorney John P. Heekin's office, superseded those proceedings.

"I truly appreciate the dedication of our state and federal law enforcement partners to target, identify, and incapacitate the sexual predators … seeking to sexually exploit and victimize kids online," Heekin said in a statement announcing the plea.

Black faces up to 10 years in federal prison on each of the five counts. His sentencing is scheduled for Dec. 3 in federal court in Florida.

Residents with information about online exploitation can contact the National Center for Missing & Exploited Children at 1-800-843-5678 or submit a tip at CyberTipline.org.