U.S. conservative activist Andrew Breitbart, a larger-than-life author and publisher, died unexpectedly of natural causes in Los Angeles early on Thursday, a representative for his website confirmed. He was 43.

The brash and outspoken writer and blogger, who was influential in U.S. Republican politics, was the center of several major news websites, including www.Breitbart.tv, www.breitbart.com and www.biggovernment.com.

We have lost a husband, a father, a son, a brother, a dear friend, a patriot and a happy warrior. 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, a memorial page on his websites said.

The page said Breitbart passed away unexpectedly from natural causes. A representative for breitbart.com confirmed his death in an e-mail.

Larry Bietz, the watch commander at the coroner's office, said it had received a report that Breitbart died at UCLA Medical Center but that the office had not yet received his body. I can confirm that it's been reported to us that he died, he said.

Breitbart reportedly collapsed when walking near his house, according to the Associated Press, which cited his father-in law.

Breitbart was notorious for his fiery opinions. The last posts from his Twitter feed appear to have come just moments before midnight, with one calling a user a putz and another replying Apologize for WHAT? to another user.

His work played a role in a number of prominent news stories over the years, including undercover videos of the community group ACORN and the texting scandal of former Democratic U.S. Representative Anthony Weiner of New York.

(Reporting By Susan Heavey; Editing by Anthony Boadle)

(This story corrects state in last paragraph)