A Dallas Independent School District student convinced a teacher to pay him $28,000 in exchange for keeping their sexual relationship a secret from police, according to court documents obtained by The Dallas Morning News.

Investigators were contacted earlier this month by a parent who said her child, a former student at Quintanilla Middle School, had been getting large amounts of money from a current teacher at the school.

Police identified the accused teacher as 27-year-old Thao Doan.

Doan admitted to conversing with the student via social media and text messages while the student was attending Quintanilla Middle School, according to police.

In court documents, Doan admits the conversations eventually turned romantic. In July 2015, Doan picked the student up at his home and drove to a nearby park, where they had sex.

The two engaged in sexual behavior on numerous other occasions in 2015.

Doan told police that in January 2016, she started receiving messages from unknown subjects demanding money. The person told her that in exchange for payment, he wouldn't tell police about the illegal relationship or release copies of the text messages between her and the student.

The demands for cash persisted throughout 2016, totaling to about $28,000, court papers show.

Doan had sex with the student again as recently as December, according to her affidavit.

Doan was arrested last week and was released after paying a $25,000 bond.

Dallas ISD confirmed to NBC 5 Doan was placed on administrative leave.