Andrew Breitbart, 43, Has Died

Conservative website publisher and author Andrew Breitbart has died. He was 43.

"With a terrible feeling of pain and loss we announce the passing of Andrew Breitbart," a statement on Breitbart's BigJournalism.com said early Thursday. "Andrew passed away unexpectedly from natural causes shortly after midnight this morning in Los Angeles."

(Related: Jonah Goldberg Breaks Down During Fox Interview Moments After Breitbart News Hits)

(Related: ‘Burn in HELL!’: Shocking Tweets Celebrate Andrew Breitbart’s Death on Twitter)

"We have lost a husband, a father, a son, a brother, a dear friend, a patriot and a happy warrior," the statement said.

Joel Pollak, editor in chief and in-house for Breitbart.com, confirmed the news to The Blaze in an email.

The Associated Press reported Breitbart was walking near his house in the Brentwood neighborhood of Los Angeles shortly after midnight when he collapsed.

Someone saw him fall and called paramedics, who tried to revive him, his father-in-law Orson Bean said. He was rushed to the emergency room at UCLA Medical Center where he died.

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

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

Larry Dietz of the Los Angeles County coroner's office told the AP a cause of death was unknown and an autopsy would "more than likely" be conducted.

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

Condolences immediately began pouring in on Twitter, a favorite social media tool of Breitbart's.

Politicians, including some of the Republican candidates for president, weighed in as well.

"RIP 'O Mighty Warrior!" Texas Gov. Rick Perry wrote on Twitter.

House Majority Leader Eric Cantor (R-Va.) wrote he was "stunned to hear about the passing of Andrew Breitbart" and offered his condolences to "his wife Susie, his children, and his friends."

Mitt Romney wrote: "Ann and I are deeply saddened by the passing of @AndrewBreitbart: brilliant entrepreneur, fearless conservative, loving husband and father."

Rick Santorum, hearing the news from reporters while on the campaign trail, called Breitbart's death "a huge loss, in my opinion for our country and certainly for the conservative movement."

Newt Gingrich called Breitbart's death "a tragedy for his family and for conservatism."

"Andrew Breitbart was the most innovative pioneer in conservative activist social media in America. He had great courage and creativity," Gingrich tweeted.

Breitbart, an outspoken critic of the mainstream media, was known for taking on his critics on Twitter and frequently re-posted their expletive-laden insults. His final tweet, posted at 11:25 p.m., was part of a similar back-and-forth discussion on the micro-blogging site.

Breitbart became well-known for his work with the Drudge Report. Shortly after the news of his death, Matt Drudge posted a personal tribute to him on his website:

DEAR READER: In the first decade of the DRUDGEREPORT Andrew Breitbart was a constant source of energy, passion and commitment. We shared a love of headlines, a love of the news, an excitement about what's happening. I don't think there was a single day during that time when we did not flash each other or laugh with each other, or challenge each other. I still see him in my mind's eye in Venice Beach, the sunny day I met him. He was in his mid 20's. It was all there. He had a wonderful, loving family and we all feel great sadness for them today... MDRUDGE

Breitbart was also involved with the Huffington Post in its early stages. Editor in chief Arianna Huffington released a statement on his passing:

I was asked many times this morning for my thoughts on what Andrew meant to the political world, but all I can think of at the moment is what Andrew meant to me as a friend, starting from when we worked together -- his passion, his exuberance, his fearlessness. And above all, what I'm thinking of at the moment is his amazing wife Susie and their four beautiful young children. My love and thoughts are with them right now.

This post has been updated since it was first published.