Simplify the following text for a Grade 8 native English-speaking person.
Original: John Fitzgerald `` Jack '' Kennedy ( May 29 , 1917 - November 22 , 1963 ) , often referred to by his initials JFK , was the 35th President of the United States , serving from 1961 until his assassination in 1963 .
Simplified: John Fitzgerald Kennedy ( May 29 , 1917 - November 22 , 1963 ) , also known as JFK , was the 35th president of the United States of America . He was in office from 1961 until he was assassinated ( shot dead ) in 1963 .