From the National Archives – – On April 4, 1968, civil rights activist Martin Luther King, Jr., was shot in Memphis, Tennessee, as he leaned over a railing at the Lorraine Motel. He was pronounced dead at 7:05 p.m. in Memphis (8:05 p.m. EST)
This page from the President Johnson’s daily diary records that LBJ was notified of the shooting at 7:24 p.m. EST. On the next page, at 8:20 p.m. EST, the Justice Department informs LBJ that Martin Luther King, Jr., has died. The next several hours are a mix of the tragic (a condolence call to King’s widow) and the mundane (family dinner) and the business of running the country (calls to the Attorney General).
http://research.archives.gov/description/192476