Dallas County Sheriff John David Mahaffey, 19, was arrested on charges he sexually assaulted another male student on the campus of Southern Methodist University.

A fourth-generation Southern Methodist University student accused of sexually assaulting another male student told the victim “you better not tell a soul” and later admitted the crime in a phone call recorded by police, according to a court document released Friday.

John David Mahaffey, 19, a sophomore finance major, has been suspended from the Sigma Phi Epsilon fraternity and banned from the University Park, Texas, campus while the investigation into the alleged assault continues.

The incident happened late Saturday night.

See more stories at NBCDFW.com

An affidavit of probable cause filed by an SMU police investigator provides graphic details.

Mahaffey forced the other student to perform a sexual act on him, the officer said.

“Victim stated ‘NO’ and ‘STOP’ several times but felt intimidated and physically forced into compliance,” the affidavit said.

The following day, the student went to police and agreed to make a recorded phone call to Mahaffey, police said.

Stay informed with the latest headlines; sign up for our newsletter

“During the phone call, the victim told the defendant, ‘You know I didn’t want to do that?’ The defendant replied, ‘I know you didn’t, but we have to say it was consensual or lawyers, parents, and the school will be involved.’”

According to police, the alleged victim was attacked twice – once in a campus parking garage and again near the fraternity.



Mahaffey, of Springfield, Mo., is a Hunt scholar, a student senator, a scholarship committee chairman, and an officer on SMU's Inter-fraternity council, according to the university website.

Watch US News crime videos on NBCNews.com



According to an article last year in SMU's student newspaper, the Daily Campus, his great-great grandfather was a member of SMU's founding committee and one of its first professors and his grandmother, father and two aunts also were students.



SMU released a short statement, confirming the arrest, and saying Mahaffey is “temporarily banned from campus pending further investigation."



Debbie Denmon, a spokeswoman for the Dallas County District Attorney’s office, said Friday that the case probably will be referred to a grand jury in the next few weeks.



Mahaffey was released from the Dallas County jail on $25,000 bond. He did not return a phone call seeking comment.

More content from NBCNews.com:

Follow US News from NBCNews.com on Twitter and Facebook