Conservative blogger and entrepreneur Andrew Breitbart died unexpectedly early Thursday, according to a notice posted on several of his websites. He was 43.

A statement said Breitbart died from natural causes shortly after midnight in Los Angeles.

The L.A. Coroner's office confirmed to ABC News Radio that Breitbart died this morning at UCLA Medical Center. His father-in-law, Orson Bean, told NBC San Diego someone saw Breitbart collapse ouside his Brentwood, Calif. home and dialed 911.

We have lost a husband, a father, a son, a brother, a dear friend, a patriot and a happy warrior, wrote Larry Solov, Breitbart's business partner. 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.

Breitbart, a father of four, was an outspoken conservative blogger known for leaking photos, undercover videos, and social commentary of the left. His last tweet, just before he died, was typical of his headstrong persona: I called you a putz cause I thought you werebeing intentionally disingenuous. If not I apologize, he wrote.

Breitbart helped launch The Huffington Post and was an editor of the Drudge Report. He established himself as a provactive and polarizing figure in conservative blogging and politics through his websites--BigHollywood.com, BigJournalism.com, BigGovernment.com, BigPeace.com and Breitbart.com--and often made headlines by putting himself in the story.

After leaking the embarrassing Twitter pictures of former Rep. Anthony Weiner that eventually led to his resignation, Breitbart famously hijacked the press conference and took questions before the Democratic congressman took the podium.

He is also known for publishing an undercover video in 2009 that exposed Association of Community Organizations for Reform (ACORN) employees giving advice to conservative activists posing as a prostitute and a pimp. The news led Congress to seek cuts to the organization's federal funding.

In 2010, he got Shirley Sherrod fired from the Dept. of Agriculture for publishing comments that were later found to be taken out of context.

A huge critic of the Occupy movement, a video of Breitbart yelling at protesters to behave themselves and stop raping people at the Conservative Political Action Conference three weeks ago recently went viral. In typical Breitbart fashion, his antics inspired passionate reaction and criticsm.

Regardless of how people felt about him, reporters agree the Breitbart was always happy to chat with journalists and bloggers. When the International Business Times last interviewed Breitbart three weeks ago at the Conservative Political Action Conference, he seemed very healthy. ABC News Deputy Political Director Michael Falcone tweeted that many journalists last spoke to Breitbart in person on Saturday during the Americans for Prosperity forum in Troy, Michigan.

Reporters and pundits mourned the writer as soon as the news broke.

I'm stunned. He was kinetic, brash, relentless, full of fight, the bane of the Left, and a mentor to the next generation of right-wing activists and citizen journalists, wrote conservative blogger Michelle Malkin.

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