LOS ANGELES - Conservative activist Andrew Breitbart, who was behind private investigations that led to the scandals surrounding former New York Congressman 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 that 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 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. His recent book is "Righteous Indignation."

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In announcing his death, a post on bigjournalism.com said, "We have lost a husband, a father, a son, a brother, a dear friend, a patriot and a happy warrior. Andrew lived boldly, so that we more timid souls would dare to live freely and fully, and fight for the fragile liberty he showed us how to love."

In New York, Breitbart is known for his involvement in the Twitter scandal that forced Weiner out of office. Weiner had sent intimate pictures of himself to online paramours who leaked the shots to Breitbart. In short order, the scandal, and pictures, were everywhere, including The New York Times.

Breitbart also was at the center of a controversial video that led to the firing of Agriculture Department employee Sherrod over what appeared to be a racist remark. Once the full story was known, President Barack Obama and Agriculture Secretary Tom Vilsack apologized for the firing and offered her jobs. She refused and is suing Breitbart.

In the video Breitbart disseminated, Sherrod, who is black, seems to make a racist remark when telling a local NAACP group that she was initially reluctant to help a white farmer save his farm when she worked as a rural development agent in Georgia.

Missing from the Breitbart 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.

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. Although there are questions about the tape's editing, it was enough for Congress to cut off grants to ACORN, effectively killing the organization.