A Warren County man who admitted sending child pornography to an undercover FBI agent was sentenced Tuesday to 20 years in prison.

Mark Allen Johnson, 31, of Rockfield, was sentenced in U.S. District Court on charges of distribution of child pornography, attempted enticement and attempted transfer of obscene material to a minor.

Johnson was the subject of an FBI investigation that culminated in his arrest last year.

According to filings in the criminal case, Johnson initiated a conversation on a dating app in 2019 with the agent, who was posing as a 15-year-old girl.

Over a two-month period, Johnson sent a number of sexually explicit messages to the agent and arranged to meet with the purported juvenile for sex, though Johnson ultimately did not travel to the location, court records show.

A criminal complaint filed against Johnson also accused him of communicating online with another detective with a Georgia law enforcement agency posing as a 13-year-old girl.

Assistant U.S. Attorney Madison Sewell filed a sentencing memorandum earlier this month that disclosed that Johnson reached out to the Georgia officer with a message that the FBI had seized his phone after executing a search warrant at his home.

“He had been talking to (the Georgia officer) for a week, with overtly sexual conversations, and on Feb. 11, 2020, he had sent her a video of child pornography,” Sewell said in the filing.

Johnson also sent a picture of the federal search warrant to the undercover officer, who contacted the FBI agent listed on the warrant.

At Tuesday’s sentencing hearing, Sewell said that the incidents involving the two officers, plus a prior incident that led to his conviction in McCracken Circuit Court in a separate case, showed that Johnson merited a lengthy prison term.

“The conduct in this case is so serious and so repeated,” Sewell said in court. “Johnson poses a grave danger to children and has shown through his conduct to be incorrigible.”

Questioned by U.S. District Court Chief Judge Greg Stivers, Sewell said the federal investigation uncovered online chats of a sexual nature between Johnson and other people, though law enforcement was unable to confirm their identities.

Johnson’s case in McCracken County stemmed from an allegation that he communicated for a week in 2016 with an undercover law enforcement officer posing as a juvenile, asking to engage in sex acts with an 11-year-old and a 13-year-old girl and traveling to Paducah in hopes of meeting with the juveniles, according to court records.

He pleaded guilty last year to a count of prohibited use of electronic communication systems to procure a minor and awaits sentencing in that case.

“I’ve been ashamed of what I’ve done,” Johnson said in court Tuesday. “I need help to get rid of the evil in my head.”

Johnson’s attorney, federal public defender Pat Bouldin, said that Johnson had long struggled with learning disabilities and was a victim of abuse as a child.

Johnson had previously attempted suicide and his mother attempted to get help for him through mental health counseling, said Bouldin, who argued for a 15-year sentence for Johnson, the mandatory minimum for his crimes under federal law.

Stivers imposed a 20-year sentence and ordered Johnson to be supervised for life once he completes his incarceration.

“There are very few things I consider more atrocious than hurting a child,” Stivers said. “One of the saving graces, I suppose in this case, is there has been no contact (with children) proven.”