Frank Sinatra Jr., son of the legendary singer, died of a heart attack Wednesday while on tour in Daytona Beach, Florida. He was 72.

His death was confirmed by the Associated Press, which received a statement from Sinatra’s family citing cardiac arrest as the cause of death.

Frank Jr.’s sister Nancy shared the news with a Facebook post, saying, “Sleep warm, Frankie…”

The younger Sinatra was kidnapped at age 19 at Harrah’s Lake Tahoe on December 8, 1963, as his father was in production on “Robin and the Seven Hoods”; Sinatra Sr. paid ransom of $240,000, and his son was released two days later. By that time, he had already begun pursuing a musical career of his own, having become the vocalist for the Sam Donahue band.

In 1988, at his father’s insistence, Sinatra Jr. put his own performing career on hold to work as Sinatra Sr.’s musical director and conductor. Frank Sinatra Sr. died in 1998. He was buried with a roll of dimes, a habit that began at the time his son was kidnapped so he could be sure he would have change for a pay phone.

Sinatra Jr. also learned the music business by spending time with Duke Ellington. By the time he was 24, he had performed in 47 states and dozens of countries. His first album was “Young Love for Sale” in 1965.

Sinatra Jr. guested on “The Smothers Brothers Comedy Hour” with sister Nancy, sang with his own band in Las Vegas casino and served as an opening act for other, bigger names.

Sinatra Jr. made some TV appearances in the 2000s, including on a 2006 episode of “Family Guy” and an episode of “The Sopranos,” and he released the 2006 album “That Face!”

In 2003 Variety‘s Richard Ginnell reviewed a concert by Sinatra Jr., declaring that “he might have had an easier time establishing himself had he gone into real estate. But his show made me awfully glad he decided music was his calling. There aren’t too many singers around with Sinatra’s depth of experience in big band music, or his knowledge of the classic American songbook. There are even fewer with such real feeling for the lyrics of a song, and such a knack for investing a song with style and personality.”

He performed one of his final Southern California concerts on Dec. 12, the centennial of his father’s birth, at the Saban Theatre in Beverly Hills. As family photos and clips were projected on screen, Sinatra Jr. sang many of his father’s standards, drawing some of his biggest applause for “One for My Baby (and One More from the Road).”