(Reuters) -Billionaire investor Bill Ackman's Pershing Square Capital Management will buy 9 million newly issued shares of real estate developer Howard Hughes Holdings for $900 million, the companies said on Monday.

Billionaire investor Bill Ackman said on Monday that he raised his stake in real estate company Howard Hughes, realizing a long-held dream of creating a diversified holding company modeled after legendary investor Warren Buffett’s Berkshire Hathaway.

Ackman, Pershing Square’s chairman and CEO, would become executive chairman of the Howard Hughes board. Hughes CEO David O’Reilly would retain his role.