A popular underground New York City rapper who performed under the stage name Pumpkinhead died early Tuesday morning at the age of 39.

Besides being a staple in the world of underground hip hop, Pumpkinhead, also known as PH, was the co-founder of label MCMI Records. His cause of death remains unknown, though Rolling Stone reports that the rapper had been admitted to a New Jersey hospital earlier in the week for minor surgery. He is survived by his wife, two sons and unborn daughter.

Born as Robert Diaz, Pumpkinhead was a native of Park Slope, Brooklyn, and was noted for his distinctive gruff voice, hilarious punchlines and humility. He went on to become a fixture on the underground and battle-rap scence for almost two decades. He also collaborated with other lyricists and veterans of indie rap, such as Talib Kweli, Royce Da 5'9", Murs, Del the Funky Homosapien, Jean Grae, Wordsworth, Immortal Technique and producer Marco, reports CNN.

"To lose such a great human being so early in his life, man. No words," Talib Kweli wrote on Instagram. "There is a fraternity of artists who were around for all of this. PH inspired us all. He will live on thru us even though his physical presence will be missed. RIP Robert Diaz."

"Pumpkinhead was as much a soldier for hip-hop as he was an artist," veteran producer and radio host DJ Eclipse told Rolling Stone. "It was his presence in NYC that I'll remember most. In the Nineties, I witnessed his come-up as a formidable opponent on the mic at many MC battles. As part of MCMI, he helped organize shows that weren't just events, but events you did not want to miss. You'll be missed my brother."

Immortal Technique also shared his thoughts about the Brooklyn rapper on Facebook, writing: "He was one of those guys who would just freestyle in the street for hours, 20 round battles, of merciless bars, and he always had a box of CD's hustling. ... PH always had jokes man. He was never unprepared to tell you about yourself."