A former Coppell teacher was arrested Wednesday on a charge of online solicitation of a minor after, according to an arrest warrant affidavit, he had sexually explicit conversations with someone he believed was underage.

But 26-year-old Steven Rhea Hart of Hurst was instead trying to arrange a sexual encounter with with an undercover detective with the Tarrant County sheriff’s office, the affidavit said. Hart resigned the same day he was arrested.

During their online chats, Hart told the undercover detective: “I’m a high school teacher lol," the affidavit said.

Hart was no longer listed Friday among inmates at Tarrant County Jail. Until his resignation, he had taught at Coppell High School Ninth Grade Campus.

It was unclear Friday whether Hart has an attorney.

Steven Rhea Hart (Tarrant County Sheriff's Office)

According to the arrest affidavit, Hart thought he was talking to a high school student Oct. 15 on the online social networking app Grindr.

In reality, he was communicating with the detective, who was posing as a teenage boy, according to the affidavit. The detective used photographs of a deputy sheriff who agreed to use his image in the undercover operation, the affidavit stated.

The suspect, who used the name “Hello,” told the undercover detective, “How are you doing? You’re Really Cute,” the affidavit stated.

When “Hello” was asked what he did for a living, he replied, “I’m a high school teacher lol.”

“Oh, ya?” the detective replied. “Well, I’m a high school student," the affidavit stated.

When “Hello” started to ask about a meeting, the conversation grew more sexually explicit, according to the affidavit.

The two exchanged messages into late February until the detective submitted a subpoena for user information connected to the suspect’s online account on Kik, an instant-messaging service.

The detective then found Hart’s name linked to the Kik account he used, the affidavit said.

Ninth Grade Campus Principal Cody Koontz sent out a letter to parents and employees notifying them of Hart’s arrest and resignation. The district also banned Hart from every campus and facility.

Hart worked for the district from 2016 until his resignation earlier this week, the district’s letter said.

If convicted, Hart faces between two and 10 years in prison and a fine of up to $10,000.