Simplify the following text for a Grade 9 native English-speaking person.
Original: John Smith ( 13 September 1938 - 12 May 1994 ) was a British Labor Party politician who served as Leader of the Labor Party from July 1992 until his sudden death from a heart attack in May 1994 .
Simplified: John Smith ( 13 September 1938 - 12 May 1994 ) was a British politician who was the leader of the Labor Party from July 1992 until his death from a heart attack .