W. Mark Felt, Sr., the number 2 man at the FBI during the Watergate scandal, died yesterday from Alzheimer's disease at a hospice near his home in Santa Rosa, California, the Washington Post reports. Felt was an instrumental player in the stunning downfall of President Nixon, but his identity as "Deep Throat"—reporter Bob Woodard's anonymous source for the Post's bombshell series of scoops on the Watergate affair in 1972—was unknown until three years ago, when Felt's family unmasked him in the pages of Vanity Fair. According to the Times, even Woodward was shocked at this; he had gaurded the secret so zealously that even his partner Carl Bernstein did not meet Felt until earlier this year. Felt never revealed why he leaked details on the Watergate break-in and cover up to Woodward, but the Times obituary points out that in May 1972 Feld had been passed over by Nixon as Edgar Hoover's successor to run the bureau.