John Ritter, the star of ABC's "8 Simple Rules for Dating My Teenage Daughter," died Thursday (Sept. 11) after collapsing on the set of the sitcom. He was 54.

Ritter was taken from the show's Burbank set to nearby Providence St. Joseph Medical Center, where he was pronounced dead about 10 p.m. PT Thursday. The cause of death was a tear in the aorta that was the result of a previously undiagnosed flaw in the actor's heart.

"All of us at ABC, Touchstone Television and The Walt Disney Company are shocked and heartbroken at the terrible news of John's passing," the network says in a statement. "Our thoughts and prayers are with his wife and children at this very difficult time."

Tracy Gamble and Flody Suarez, executive producers of "8 Simple Rules," echoed those sentiments, calling Ritter a "force of nature."

"He'd sweep onto a quiet set and it would instantly turn into a laugh-filled room," the producers say in a statement. "For everyone here, coming to work each day was a joy. ... We will miss his smile, we will miss his laugh and, mostly, we will miss his incredible kindness."

Ritter's son Jason, who followed his dad into acting, says he learned a lot about show business from his dad, even though at first John was less than thrilled with the idea of his son following in his footsteps.

"My dad's dad was an actor," -- movie cowboy and country-music star Tex Ritter -- "and he did not want his son to be an actor," Jason Ritter told Zap2it during interviews for his movie "Freddy vs. Jason." "But my dad said he would support me when I said I wanted to pursue it. ...

"The thing I owe the most to my dad is how he helped me analyze and discuss movies together. I'll never forget that," says Jason Ritter, who also co-stars in CBS' "Joan of Arcadia." "We'd talk about movies even when I was a young kid, and we'd analyze why it works and how things are done."

John Ritter was born Sept. 17, 1948, and grew up in Los Angeles. He graduated from the University of Southern California and started in Hollywood in the early 1970s. His first major role came on "The Waltons," where he played a minister from 1972-77.

In 1977, he took a starring role in "Three's Company," which quickly became a hit and made Ritter a TV star by showcasing his talent for physical comedy. He earned three of his five career Emmy nominations for playing would-be Lothario Jack Tripper, winning the award for lead actor in a comedy in 1984. (The others were for "Hooperman" in 1988 and a guest role on "Ally McBeal" in 1999.)

He returned to sitcoms last year with "8 Simple Rules," which performed well for ABC and was considered a linchpin of the network's schedule. The comedy's second season was scheduled to begin Tuesday, Sept. 23; there is no word yet on whether the series will air as scheduled.

The series also marked Ritter's return to TV comedy for the first time since his series "Hearts Afire" went off the air in 1995. He took a number of dramatic roles in the intervening years, including "Sling Blade" and a recurring part on The WB series "Felicity."

In addition to Jason, Ritter is survived by his wife, actress Amy Yasbeck; their daughter Stella; and two other children from his first marriage to Nancy Morgan, Carly and Tyler.