A former Fort Worth high school drama teacher exchanged nude photographs and videos with a 15-year-old boy from Michigan and told authorities the teen was his boyfriend, the U.S. attorney’s office said Tuesday.

Matthew Anthony Keller, 24, was arrested last week. He faces a charge of receipt of child pornography, which is punishable by up to 20 years in prison. He remains in federal custody with a detention hearing set for Wednesday.

Keller, a Watauga resident, and the teen exchanged photographs and videos for about 18 months after meeting in an online chat room when the boy was 13, according to a federal complaint.

Last month, Keller resigned voluntarily from his job as a theater director at Southwest High School, school district spokesman Clint Bond said.He was hired by the district in August 2014, spending his first year at South Hills High School before moving to Southwest.

The complaint also referred to Keller as a youth pastor.

Keller volunteered in the children’s ministry at Haltom Road Baptist Church in Haltom City but was not an employee, the church said in a statement. Keller has been removed from all duties at the church and restricted from entering the church.

“At this time, we are not aware that [Keller] behaved inappropriately with anyone” at the church, the church’s statement said.

Keller’s public Facebook page indicates he was active in staging and performing plays at the church as recently as November 2015.

After the Michigan boy’s parents discovered the relationship with Keller, the boy filed a report with authorities on June 7, according to the federal complaint. The parents also discovered that Keller planned to fly to Michigan, possibly to meet the boy for sex.

Investigators with the Macomb County Sheriff’s Department in Michigan assumed the boy’s identity and began texting Keller on the boy’s cellphone.

Keller “appeared skeptical and requested a video chat to prove it was the victim,” according to the complaint.

Investigators then made direct contact with Keller, who acknowledged meeting the boy online about two years ago.

Keller said he considered the teen to be his boyfriend and “described their communications and conversations as sexual in nature,” the complaint said.

Keller said the teen sent him about 25 nude photos and 25 nude videos.

The boy told authorities that he told Keller he was 18 when they first met before admitting a few months later he was 13. The boy said Keller was “very suspicious” and would request pictures of the boy’s face and video chats to prove his identity.

The boy told authorities that he and Keller sexted a couple times a week and that Keller told him to delete pictures and videos.

Last week, Tarrant County authorities searched Keller’s home in Watauga and found a “mostly nude” video of the boy from November 2014 on Keller’s computer.