Note that in the five years since the assassination of JFK, CBS has changed its graphics. Although they still use a modification of the repeating "CBS News" script, it is now a "Special Report" rather than a "Bulletin," a convention which is more or less standard today. As a matter of fact, I can't recall the last time I saw an actual bulletin on TV*; the going concern nowadays is "Breaking News."
*Actually, I think I do - it was in 1981, when ABC interrupted with the shooting of Ronald Reagan.
Martin Luther King, Jr. was not an elected official, a head of state or government; yet, such was the impact he made that his murder caused regular programming to be pre-empted, and his funeral would cause the Academy Awards to be postponed for two days.