The 1968 California Democratic Party primary election took place on June 4, and is infamous because of the tragic assassination of Robert F. Kennedy in the kitchen of the Ambassador Hotel after his victory speech after midnight on June 5. In the days before 24 hour news channels, most Americans didn't find about about this event until the next morning in the newspaper.
Kennedy entered the Democratic primaries after Eugene McCarthy had proven Lyndon Johnson beatable after McCarthy's narrow loss in the New Hampshire primary in mid-March of 1968 (yes, kids, we use to have an primary election season that only lasted four months). Kennedy did not have enough delegates to win the nomination outright going into the July convention in Chicago, but he did have the backing of many old-line Democrats, including Chicago mayor Richard J. Daley.
That convention fight was ended by an assassin's bullet. Sirhan B. Sirhan, a Palestinian, sits in a California prison after being convicted for this crime; there are those who claim that he was not the triggerman, or that there were others involved. LA police found an entry in Sirhan's diary that noted "RFK must die before June 5"--the one year anniversary of the Six Day War. Sirhan was the one grabbed by eyewitness Roosevelt Grier, a member of the (then)-Los Angeles Rams' "Fearsome Foursome."
I would like to leave you with a speach that RFK made in the aftermath of an earlier tragic assassination in April of 1968.