WASHINGTON, May 19- Deputy Attorney General Rod Rosenstein knew President Donald Trump was going to fire FBI chief James Comey before he completed a memo outlining his own concerns about the former FBI leader, according to a statement obtained by NBC News. 'I informed the senior attorney that the president was going to remove Director Comey, (and) that I was writing a memorandum to the attorney general summarizing my own concerns,' Rosenstein said in the statement, referring to a Justice Department attorney. The statement was prepared for delivery to lawmakers.
