We're saddened to report that actor Robert Stack, known to generations as lawman Eliott Ness on the ground-breaking television series The Untouchables, passed away this Wednesday at the age of 84.

According to the New York Times, Mr. Stack, who had radiation treatment for prostate cancer last year, was found dead by his wife, Rosemarie, who told The Associated Press the cause was heart failure.

Stack first found success as an actor in the feature film First Love (1939), a romantic musical starring Deanna Durbin. He also appeared in such films as Mortal Storm (1940), Badlands of Dakota (1941) and Eagle Squadron (1942). His acting career was momentarily sidetracked by World War II, during which he served as gunnery instructor in the U.S. Navy. After the war, he made Fighter Squadron (1948), Date with Judy (1948), The Bullfighter and the Lady (1951); Bwana Devil (1952); War Paint (1953); and Conquest of Cochise (1953). He received an Academy Award nomination for his performance Written on the Wind (1956), and then went onto make The Last Voyage (1956).

London's Electronic Telegraph reports that it was in 1959 that pioneering producer (and I Love Lucy star) Desi Arnaz approached Stack with the idea of making a television series about Eliot Ness. Stack, the site said, was originally against the idea since he considered himself a film star and there was much less back-and-forth between the two mediums then. After seeing scripts for the series, though, he changed his mind.

“He had little in common with Eliot Ness apart from a passion for heavy-duty firearms,” the Telegraph reported. “While Ness was a devotee of the machine gun, Stack preferred a rifle, and was for several years the national sharp-shooting champion of the United States.” He won an Emmy for the role in 1960.

“Bob inhabited that role. It was flawless. He was Eliot Ness, and we just followed his lead,” actor Paul Picerni, who portrayed federal agent Lee Hobson on the show,” told USA Today. “The violence was quite controversial at the time. But at the height of that, I remember a priest said to me that The Untouchables is like a passion play. The bad guys are very bad, and the good guys are very good. It's a real lesson in life, unlike today where the bad guys often win.”

“The series was controversial in its day, mostly for its florid violence, which went far beyond what audiences then expected. Some Italian-American groups also objected to being typecast as villains,” the New York Times reported.

After the series ended in 1963, Stack had trouble getting away from the typecasting his tough portrayal of Ness engendered. He had two short-lived series (Most Wanted and Strike Force) and a number of film appearances (including Uncommon Valor) before turning his tough guy image on end with a comedic performance in Airplane!

An entire new generation of fans came to know him as the host of the long-running Unsolved Mysteries program.

“Robert Langford Stack was born in Los Angeles on January 13 1919, the son of James Langford Stack and his wife Elizabeth, an aspiring opera singer. Stack's great-grandfather arrived in what was then the village of Los Angeles in 1849, and set up the community's first theatre. Both his grandparents had been Italian opera singers,” the Telegraph reported. “Because Robert's mother wanted to study opera, Robert grew up in Paris and Rome, learning to speak both French and Italian fluently; he was still unable to speak English when, aged seven, he returned to America. As a teenager he showed considerable talent as a sportsman: he and his brother won the International Outboard Motor Championships in Venice, and remained speedboat racing champions in America for three years. At 16 Robert became a member of the All American Skeet Rifle Team; he set two world records and became National Skeet Champion.”

He is survived by his wife Rosemarie (they were married in 1956), and their son and daughter.