The NYPD announced Saturday that they had a suspect in custody, whom they believe is responsible for Sibley's death. The unidentified perp is a 17-year-old boy, per cops, and he's being charged with murder ... which NYPD says is being prosecuted as a hate crime.

The suspect surrendered Friday in Brooklyn, accompanied by a lawyer. He'd been on the police's radar since the July 29 incident ... as they believed he went to school in the area. So far, he's the only one being charged, although it's unclear if he'll be tried as an adult.

The fact this is being pursued as a hate crime lends credence to what friends of Sibley's -- some of whom say they were actually there at the gas station that night -- have been saying on social media ... namely, that the suspect and whatever group of people he was with apparently had an issue with Sibley and co. being gay. It led to a full-blown shouting match, and an eventual scuffle that resulted in Sibley being stabbed ... which was caught on video.

Based on reports, it sounds like the whole thing emanated from Sibley and his friends dancing in the parking lot ... and playing Bey's music in the background. The singer paid tribute to Sibley after hearing about it -- she has his name up on her website's homepage.

Since his death, tons of people have been paying their respects in a number of ways -- including visiting the site of his murder and voguing/protesting en masse, in his name.