Joel Pollak, the editor of Breitbart's Big Journalism website, confirmed the news, which was first posted on Big Journalism. Pollak wrote that Breitbart died of natural causes, and the Associated Press reported that he collapsed while out on a walk.

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

Also read: Why Andrew Breitbart Raged Against the Left

Breitbart, a Los Angeles native and Tulane graduate, became one of the more recognizable conservative figures in the media world. He was a regular on Fox News and other news channels, a fixture at Tea Party events and an Internet entrepreneur.

He then founded Breitbart.com in 2005 and later launched BigHollywood.com, BigGovernment.com, BigJournalism.com and other sties. They mixed right-leaning commentary with aggregation of other stories and original reporting.

He uncovered or inserted himself into a series of major political stories over the past few years, including the Anthony Weiner scandal and the unwarranted firing of Agriculture Department official Shirley Sherrod.

"He loved nothing more than to be in the middle of it," Sean Hannity said Thursday on Fox News.

In the case of Weiner, Breitbart broke the news that the New York congressman was sending lewd photos to women. That eventually led to Weiner's resignation.

In the case of Sherrod, Breitbart posted videos that appeared to show Sherrod, an employee at the Department of Agriculture, making racist remarks. That led to her dismissal. Yet after the full video aired, it became clear that Breitbart edited the clips, prompting Sherrod to sue for defamation.

Also read: Notable Celebrity Deaths of 2012

Breitbart was combative to the end. Just hours before his death, he argued over his Twitter account about the antics of conservative activist James O'Keefe, who has posted recordings embarrassing ACORN employees and NPR executives. Breitbart made a deal with O'Keefe to post O'Keefe's videos on his site.

Both Breitbart and O'Keefe relished taking on the mainstream media, big government and left-wing politicians.

Rebecca Mead wrote this about Breitbart in a New Yorker profile from May 2010:

"He does not pretend to be an expert in policy, or to be particularly interested in it. 'Just because I am paying attention to politics and culture doesn’t mean that I should be talking about the health-care bill, talking about the minutiae,' he told me. Instead, Breitbart is obsessed with wresting control of the political narrative from the established media organizations."

Breitbart was born Feb.