Kaseem Ryan, who built a small but fervent following as an underground Brooklyn rapper known as Ka while maintaining a career as a New York City firefighter, died in the city on Saturday. He was 52.

His death was announced by his wife, Mimi Valdés, on Instagram, as well as in a statement posted on his Instagram page. No cause was given, though the statement said that he had “died unexpectedly.”

First with the mid-1990s underground group Natural Elements, and then on 11 solo albums he produced himself and released over nearly two decades, Ka gripped hard-core hip-hop listeners with gloomy beats and vivid descriptions of street life and struggle.

In a 2012 review of his second album “Grief Pedigree”, The New York Times pop music critic Jon Caramanica described Ka as “a striking rapper largely for what he forgoes: flash, filigree, any sense that the hard work is already done.”

Kaseem Ryan was born in 1972 and raised in the Brownsville neighborhood of Brooklyn in New York. During his teen years, he dealt crack and sold firearms.

He spent much of the 1990s trying to make a name for himself as a rapper, but then quit music altogether, only to come back a decade later.