Frank Sinatra, Jr., the son of the legendary singer who followed his father into the music business, died while on tour. He was 72. The singer died unexpectedly Wednesday of cardiac arrest in Daytona Beach, Florida, the Sinatra family said in a statement. No other details were provided. Sinatra Jr. was famously kidnapped at 19 in 1963 and released after his father paid a $240,000 ransom. In his father’s last years of touring, Sinatra Jr. served as his dad’s bandleader. He released about six albums over the span of his career.