After a two-day trial, a former security guard for Chester High School was convicted of sexually assaulting a 16-year-old girl at his home last July, filming the encounter, and threatening her with a gun, the Delaware County District Attorney's Office said Monday.

Namar Ikeam Plummer, 28, of Marcus Hook, was found guilty by a jury of sexual assault and sexual abuse of a child for creating child pornography, authorities said. Plummer, who will have to register for life as a sex offender, faces up to 30 years in prison.

After Plummer recorded the sexual assault, it was shared last August by others — authorities say they don't know who — on Facebook and Snapchat.

The girl, who knew Plummer as "Mar" through his security guard job, complied with the sexual assault because she feared for her safety and her family's safety, authorities said.

"The victim demonstrated incredible courage by coming forward and providing detailed testimony, ensuring that the defendant will be held accountable for his actions," District Attorney Katayoun M. Copeland said in a statement.

Prosecutors did not say whether Plummer was a public employee or the employee of a private security company contracted with the Chester Upland School District at the time of the assault. Emily Harris, a spokeswoman for the District Attorney's Office, said the agency "was not able to confirm the defendant's employment details."

An administrator for the district was not immediately available for comment.

Until he is sent to state prison, Plummer is being held at the George W. Hill Correctional Facility. He is scheduled to be sentenced Oct. 23.

Authorities ask that anyone who may have been victimized by Plummer or has information about the case call the District Attorney's Criminal Investigation Division's Child Abuse Unit at 610-891-4700.