Famed “ER” actor-turned-rapper Deezer D has passed away at the age of 55.

On Thursday night (Jan. 7), TMZ reported that Deezer D, who was born Dearon Thompson, was found unresponsive at his home in Los Angeles. As of this report, Thompson’s cause of death has not been determined. However, according to Thompson’s brother Marshawn, the family believes that Deezer may have suffered from a heart attack. Back in 2009, Thompson had major heart surgery to fix a leaky heart valve and replace his aorta. However, there’s still no confirmation that Thompson’s death had anything to do with the actor-rapper’s previous surgery.

“I have a heart valve that is leaking and the aorta had expanded to way beyond what it is supposed to be,” Thompson told Radar Online of the surgery in 2009 according to the Daily Mirror. “As soon as the doctor identified what was going on, he put me in here… What I was going through for the last year—that was scary. I’m fearless about the surgery.”

Thompson began his acting career in the early ‘90s in films like CB4 before landing his most notable role as Malik McGrath on NBC’s “ER.” During his 15-year run on the show, Thompson also starred in other films like Fear of a Black Hat (1994), Romy and Michelle’s High School Reunion (1997), Bones (2001) with Snoop Dogg, Bringing Down The House (2003) with Queen Latifah, and In The Mix (2005) with Usher.

In 2008, Thompson officially launched his career in music with the release of his album Delayed, But Not Denied. The album has 14 tracks including songs like “Hollygood Livin” and “Don Dadda.” According to the Daily Mirror, Deezer said that music was always his first passion, but he made more money as an actor.

“The music thing came so natural,” Deezer said. “It actually came first, but I got paid as an actor first.”

Before his death, Thompson was teasing new music on his Instagram account. Hopefully, his family will find a way to release it in his honor.