He had grown close to Breitbart and was urging the writer to expand his website, which originally operated out of Breitbart's basement. As part of that effort, the Mercers invested $10 million in the enterprise in the summer of 2011, according to a person familiar with the transaction. When Breitbart died of a heart attack the following March, Bannon became executive chairman of the news outlet. The Mercers' co-ownership of Breitbart News, along with chief executive Larry Solov and Breitbart's widow, Susannah, was confirmed by the company last month.