WASHINGTON (AP) — Conservative media publisher and activist Andrew Breitbart, who was behind investigations that led to the resignations of former Rep. Anthony Weiner and former U.S. Agriculture Department official Shirley Sherrod, has died in Los Angeles. He was 43.

Breitbart's website, bigjournalism.com, announced Thursday he died of natural causes in Los Angeles in the early morning hours. His death was confirmed by Breitbart.com editor-in-chief Joel Pollak, who said he was at the hospital, and by the Los Angeles County coroner's office.

Breitbart was walking near his house in the Brentwood neighborhood shortly after midnight Thursday when he collapsed, his father-in-law Orson Bean said.

Someone saw him fall and called paramedics, who tried to revive him. They rushed him to the emergency room at UCLA Medical Center, Bean said.

Breitbart had suffered heart problems a year earlier, but Bean said he could not pinpoint what happened.

"I don't know what to say. It's devastating," Bean told The Associated Press.

He is survived by his wife Susannah Bean Breitbart, 41, and four children.

Breitbart was an outspoken critic of the mainstream media but was lionized by his fans for his efforts at exposing government corruption and media bias.

Breitbart was at the center of two video controversies in recent years — one that led to the firing of an Agriculture Department employee over an edited video of what appeared to be a racist remark, and another that embarrassed the community group ACORN when workers were shown counseling actors posing as a prostitute and pimp.

Breitbart is known for disseminating an edited video that showed an Agriculture Department employee making what appeared to be racist remarks.

Sherrod, who is black, was fired from her job as Georgia state rural development director in July 2010 after the video surfaced. She is seen telling a local NAACP group that she was initially reluctant to help a white farmer save his farm more than two decades ago, long before she worked for USDA.

Missing from the clip was the rest of the speech, which was meant as a lesson in racial healing. Sherrod told the crowd she eventually realized her mistake and helped the farmer save his farm. She has since filed a lawsuit against Breitbart.

Breitbart's websites also featured a 2009 hidden-camera sting video that brought embarrassment to the community group ACORN. The videos show ACORN staffers offering advice on taxes and other issues to actors posing as a prostitute and pimp.