From the article it sounds like a heart attack, though no cause has yet been mentioned.
http://news.yahoo.com/blogs/cutline/andrew-breitbart-died-los-angeles-144221781.htmlAndrew Breitbart, the outspoken conservative writer, activist and website operator, has died unexpectedly in Los Angeles, where he lived with a wife and four young children. He was 43.
Breitbart, who may have been best known as the conservative who brought down New York Rep. Anthony Weiner, was pronounced dead at the UCLA Medical Center shortly after midnight, the Los Angeles County coroner's office told Yahoo News. The cause of death was not immediately known, a spokesman at the coroner's office said.
One of his websites, BigGovernment.com, announced his death early Thursday.
"Andrew passed away unexpectedly from natural causes shortly after midnight this morning in Los Angeles," the note on his website 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."
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