A New York man who allegedly stabbed a 17-year-old girl and then posted photos of the murder on social media pleaded guilty in connection with her death Monday.

Brandon Clark, 21, of Cicero in central New York, was set to stand trial later this month on a second-degree murder charge for the killing of Bianca Devins. Prosecutors said he slit her throat on July 23, 2019, after the couple returned to Oneida from a concert in New York City.

They got into an argument after Devins reportedly kissed another man, investigators said.

Clark apologized in court Monday, saying Devins “didn't deserve what happened to her.” Authorities said the pair were friends and not romantically involved.

Clark posted photos of the murder online and then called 911 to report his crime after authorities began receiving calls about the photos. He was found by police after unsuccessfully trying to slit his own throat.

He also allegedly laid down on a green tarp -- under which Devins' body was located -- and took selfies before officers took him into custody, authorities said.

Prosecutors said the pair met through Instagram early last year and were at some point "acquainted with each other’s families.”

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Devins' mother, Kim Devins, has been advocating for new laws to prevent the posting of graphic photos like those of her daughter.

Clark is scheduled to be sentenced on April 6. He faces 25 years to life in prison.

Fox News' Nicole Darrah and The Associated Press contributed to this report.