Conservative blogger and author Andrew Breitbart has died at the age of 43. According to his website Big Government, he died unexpectedly from natural causes shortly after midnight this morning in Los Angeles. The LA Coroner's Office has since confirmed his death.

Breitbart's father-in-law Orson Bean told AP that Breitbart was walking near his house in the Brentwood neighborhood shortly after midnight Thursday when he collapsed. Someone saw him fall and called a paramedic, they rushed him to UCLA Medical Center. Bean said Breitbart had suffered heart problems a year earlier. Fox News reporter Todd Starnes tweeted Rick Santorum's response to his death: "Oh, I'm crestfallen, that's horrible...What a huge loss, in my opinion for our country, and certainly for the conservative movement."

After being inspired by The Drudge Report ("I thought what he was doing was by far the coolest thing on the Internet. And I still do") and working as an editor for the site, Breitbart launched several conservative websites of his own starting in 2005, including Breitbart.com, Breitbart.tv, Big Hollywood, Big Government, Big Journalism, and Big Peace. His sites have provided a mix of aggregated news and right-leaning commentary and original reporting. Breitbart had made it his mission to expose and counter what he saw as the leftist bias of American media institutions.

Among his claims to fame, Breitbart's websites hosted a series of videos made by James O’Keefe in which he dressed up as a pimp and tried to get housing and business aid from community organizers Acorn. Breitbart was also the person who leaked several nude photos of former Congressman Anthony Weiner, which ultimately led to his resignation—Breitbart even showed up at Weiner's press conference and demanded an apology for saying he was a liar (which Weiner did).

Breitbart gained much notoriety from the frequent media stunts he pulled as well—just a few weeks ago, he was captured on camera unleashing his fury at Occupy demonstrators, "calling them 'freaks and animals' at the top of his lungs." In a feature piece on him from 2010, the New Yorker described him as a cultural warrior not particularly interested in the minutiae of policy, more invested in "judgmentalism" and taunting his enemies:

No battle is too petty for Breitbart, no target too small or pathetic. He once showed me a series of messages that he had received from an apparently unhinged visitor to his Web sites. One missive concluded with a postscript: “You drank human urine three times—how did it taste?” Breitbart recalled, “That is when I said, O.K., I am not going to ignore him anymore—I want to create a level of pain for him that makes him realize this is not worth this.” He published the messages, as well as the sender’s name and photograph, on Big Journalism, along with a scathing editorial saying that the sender’s “stylings deserve a far greater public platform.” Breitbart told me, “I am sure if you talk to shrinks, or prosecutors, who are experts in these types of people, it is best to avoid them. But that’s not how my brain works.”

You can listen to what appears to be his last interview—debating the Occupy movement in a heated exchange on WKRO radio—here.

Many media members and pundits are weighing in on Breitbart's death. Liberal media watchdog Media Matters said: "We've disagreed more than we've found common ground, but there was never any question of Andrew's passion for and commitment to what he believed." Arianna Huffington, who hired Breitbart to help launch The Huffington Post, gave this statement about his death:

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.

Glenn Beck, who had a public falling out with Breitbart, said on air this morning: “Andrew and I were not close. I met Andrew on several occasions, and it’s a shock that he’s dead.” Matt Drudge, publisher of the Drudge Report, posted a statement on his site about his former protege:

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

Sarah Palin made a long post on her Facebook page: "We are all stunned and saddened by the news of Andrew Breitbart’s passing. Andrew was a warrior who stood on the side of what was right. He defended what was right. He defended the defenseless."