MS-13 gang members filmed themselves killing a 15-year-old girl in January in a brutal attack carried out with a knife and a large wooden stake, according to disturbing testimony from an FBI agent.

Jose Cerrato, a 17-year-old member, was barking out orders and narrating as he made the recording with a cellphone to send to MS-13 leaders in El Salvador who sanctioned the killing, FBI agent Fernando Uribe said in testimony Monday in a Virginia court, the Washington Post reported.

The girl, Damaris Reyes Rivas, of Gaithersburg, Md., was killed Jan. 8 in a Virginia park. Authorities found her body buried under railroad ties a month later. She had been stabbed numerous times.

It’s unclear if the video was ever sent to El Salvador, but Uribe testified that Cerrato was promoted in the gang for his role in the murder, the paper reported.

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Uribe testified before a judge weighing whether Cerrato should be tried as an adult on murder, abduction and gang participation charges. After the testimony, the judge ruled Cerrato could.

Cerrato is one of 10 MS-13 members — four adults and six teens — charged with Damaris’ death. Of the 10, four were in the country illegally.

Her alleged killers believed she lured another MS-13 member, 21-year-old Christian Sosa Rivas, to his death a week earlier, The Post reported. Eight people have been charged with that killing.

“If someone dies in a clique as a result of a fellow member, the person is killed in retaliation,” Uribe testified, according to the paper.

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The paper reported that the two killings highlight an MS-13 resurgence in the DC area — and the gang’s brutality in enforcing internal discipline.

Uribe testified that Cerrato sought to get Damaris to admit on video that she played a role in the murder of Sosa.

He said at one point Damaris was forced to take off her clothes on the frigid day so “she could feel the cold that Christian did,” according to the paper.