A Sumner County man, authorized to be a substitute teacher, is now behind bars facing federal child pornography charges.
School officials say Robert Johnson passed a background check, and could have been called to teach, but that never happened and now never will.
Johnson, 43, was indicted earlier this month on the child porn charges and has already been convicted of three counts of having inappropriate sexual communications with a 12-year-old girl on Facebook.
According to investigators, Johnson was identified by the girl's mother who noticed inappropriate Facebook chats between him and her daughter in March.
Gallatin police officer Bill Storment called Johnson an acquaintance of the victim's family and said the two met at a local Karate studio.
Storment said Johnson requested the juvenile's friendship on Facebook and began "sending inappropriate messages and explaining explicit symbols and language to the child."
Johnson was charged with multiple counts including providing obscene material to a minor. Storment said investigators had no reason to believe there was any physical contact between the girl and Johnson.
Johnson eventually pleaded guilty to the crimes and began serving his sentence.
"The suspect was asked, ‘Is it appropriate to have this type contact with a 12-year-old?' and he said, ‘No, it is not,'" Storment recalled.
At approximately the same time, the FBI executed a search warrant at Johnson's North Water Avenue apartment.
There, federal agents seized computers that investigators say Johnson used to download and disseminate child pornography.
On August 22, he was indicted by a federal grand jury on three counts of child pornography.
"Anytime you have an adult making a victim of a vulnerable child we want to make sure that is exposed," Storment said.
Investigative sources say prior to his arrest, Johnson had put in an application to be a substitute teacher with the Sumner County school system.
Public information officer Jeremy Johnson admits that the system was unaware of his criminal status until News 2's phone call.
"He was hired in March and he passed a background check in March and was put on an approved list but he didn't work for us," Johnson said, adding, "He never received a check and we are in the process of verifying these charges and when we do he will be pulled off our substitute list."
Johnson is currently serving his state charges in the Sumner County jail.
He was sentenced to five years in prison, four-and-a-half of which was suspended.
If convicted on the federal porn charges, Johnson could be spending many more years behind bars.
Andy Cordan is following this story and will have more tonight on Nashville's News 2 at 6 p.m.