John Ritter, the Emmy-award winning star who became a household name playing bumbling wannabe-Casanova Jack Tripper on '70s TV hit Three's Company, died suddenly from an arterial problem, according to published reports. He was 54.

Ritter collapsed Thursday while on the set of his ABC comedy 8 Simple Rules for Dating My Teenage Daughter. He was taken to Providence St. Joseph Hospital in Burbank, Calif., but surgeons there were unable to save him. He died from a "dissection of the aorta," a previously undetected flaw in the main artery from the heart, according to his publicists.

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

"It's just stunning, unbelievable," Susan Wilcox, his assistant of 22 years, told the Associated Press. "Everybody loved John Ritter. Everybody loved working with him. ... Whatever set he was working on, he made it a very fun place."

Ritter has been a familiar face to TV audiences since starring on Three's Company, which has endured over the past two decades in syndication. His role on that show – as a bachelor who shares an apartment with two young single women, considered risque when it first aired – brought Ritter fame as well as Emmy and Golden Globe awards.

He has worked consistently since Three's Company was canceled in 1984, starring in more than 25 TV movies and on series such as Hooperman in the late 1980s and Hearts Afire in the early 1990s. He also appeared on the big screen in movies such as 1996's Oscar-winning Sling Blade and 2002's Tadpole, and performed on Broadway in Neil Simon's The Dinner Party, AP noted. He described his movie career as "peaks and valleys" and his TV work as "a big mountain" to PEOPLE in 2002.