At the moment the coroner is investigating the cause of his death, and the official announcement will probably not be made for several weeks. According to friends he was walking when he just collapsed, and although he was taken to hospital it was too late to save him. It seems he had a heart problem about a year before this, and the description of the cause seems to fit with its being a heart attack; we will know for sure in a few weeks.

Since Breitbart died there have been some very wild and silly conspiracy theories on the web. Nobody has been able to find evidence for any of these. To me, it all sounds very much like the conspiracy theories that abounded when Stieg Larssen died in rather similar circumstances. Of course politically the two men were total opposites, but because they were both controversial figures and died quite young, a lot of people just couldn't accept that they died of natural causes.