Former MSNBC host and longtime radio broadcaster Ed Schultz has died. He was 64.

Schultz, a liberal firebrand, died of natural causes, according to WDAY-TV, where he had once worked.

Schultz is most known for his stint as the host of the Ed Show, which aired on MSNBC from April 2009 to July 2015. Most recently, he hosted News with Ed on RT America, part of the Moscow-backed RT network that has been criticized as pushing Russian propaganda and was forced to register as a "foreign agent" by the Justice Department in 2017.

Schultz was an outspoken critic of Vladimir Putin during his time on MSNBC, but once he joined RT America in January 2016, he repeatedly dismissed intelligence assessments that Russia interfered in the 2016 election through social media posts and the hacking of DNC emails.

"We at RT America are sad to announce the passing of Edward Andrew Schultz," RT said in a statement. "Ed Schultz passed quietly early morning on July 5 at his home in Washington, D.C. This announcement comes as a shock to all of us here at RT America."

MSNBC's Steve Kornacki broke into coverage Thursday afternoon to break the news of Schultz's passing.

Schultz got his start on radio and TV as a sportscaster in Fargo, N.D., but developed a national following once he became more focused on politics. At one point, The Ed Schultz Show was syndicated to nearly 100 affiliates, and in 2008 he was ranked No. 17 nationally by Talkers magazine, reaching a weekly audience of more than 3 million listeners.

"Ed Schultz was incredibly kind to me when I was first doing TV on MSNBC," Sam Stein, the politics editor at The Daily Beast and an MSNBC contributor, wrote on Twitter. "He used to do shows from clinics where doctors gave free care to the indigent. No one else would do that. RIP."