The rap genre lost one of its up-and-coming artists on Wednesday.

Fast-rising rap artist Gustav Ahr, or "Lil Peep" passed away before his show on Wednesday night at The Rock, with the exact cause of his death still under investigation.

The 21-year-old New York artist was pronounced dead at 9 p.m., according to the county's medical examiner, with The New York Times reporting that the rapper died from overdosing on the anti-anxiety medication, Xanax.

Lil Peep was best known for his songs "White Wine," "Benz Truck," and "The Way I see Things," which have gone viral on YouTube, with upwards of 12 million views per track.

Ahr was born on Nov. 1, 1996, and took to recording tracks after dropping out of high school, making music through online sites like SoundCloud and YouTube.

He released his first mixtape, Lil Peep Part One, in 2015—with his debut album,. Come Over When You're Sober released on June 2.

Ahr was known for the multi-instrumental aspect of his work, playing trombone and tuba on many of his tracks, and frequently described the close relationship he had with his mother, Liza, in many of his songs.

In all, Ahr released four mixtapes, one album and six EPs in his brief career, having been described as "The future of emo," by music magazine Pitchfork.