NEW YORK (AP) — Rapper Tekashi 6ix9ine (six-NYN') is testifying against two reputed members of a violent New York City street gang.

The rapper took the witness stand Tuesday as part of an agreement with federal prosecutors.

He admitted in a guilty plea this year that he joined the Nine Trey Gangsta Bloods and helped try to kill a rival gang member.

One of the defendants, Anthony Ellison, is accused of kidnapping and robbing 6ix9ine last year after a falling-out. Ellison denies the charges.

6ix9ine's decision to cooperate has upended his bad boy image on social media. Rap icon Snoop Dogg recently labeled him a "snitch."

The 23-year-old rapper's album "Day69: Graduation Day" was among the top sellers on iTunes following its release last year.

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This story has been updated to correct the spelling of the rapper's name in the headline to 6ix9ine, instead of 6six9ine.