Final answer:
Medgar Evers, the NAACP field secretary in Mississippi, was murdered on the night of Kennedy's televised speech in June 1963. He was killed by Byron de la Beckwith, a white supremacist.
Step-by-step explanation:
The individual murdered in June 1963 within a few hours of Kennedy's televised speech to the nation was Medgar Evers. Evers was a renowned civil rights activist and the NAACP field secretary in Mississippi. On the very day of President Kennedy's announcement of new civil rights legislation, Evers was shot and killed in the driveway of his home in Jackson, Mississippi by white supremacist Byron de la Beckwith. Evers had played a significant role in the fight for civil rights, encouraging African Americans to vote and actively participating in the movement. Medgar Evers assassination was a significant blow to the civil rights movement.
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