Frank Sinatra's son, Frank Sinatra Jr. has died unexpectedly at the age of 72 after suffering a massive heart attack while on tour in Florida. 

Members of his family along with his manager, Andrea Kauffman, confirmed the sad news. Singer Nancy Sinatra posted a message on Facebook page to tell fans that her brother died of cardiac arrest and she wrote, "Sleep warm, Frankie..." 

Frank Sinatra Jr. was kidnapped and held for ransom when he was 19 in 1963, but escaped his captors and was found walking the streets of Bel Air, Los Angeles. His kidnappers were later convicted.

Last summer, he delighted sports fans by performing the American National Anthem at a New York Yankees game. Sinatra, Jr. was in Daytona Beach, Florida preparing for a concert on his "Sinatra Sings Sinatra" tour when he fell ill on Wednesday afternoon (March 16).

He was the son of Frank Sinatra and his first wife, Nancy, and the brother of singer and actress Nancy Sinatra and TV producer Tina Sinatra.

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