"I thought that if were going to show this, we should SHOW it," Penn recalled. "We should show what it looks like when somebody gets shot."
His cinematic art, he noted, only reflected the times: TV coverage of Vietnam "was every bit, perhaps even more, bloody than what we were showing on film."
The director died Tuesday night, a day after his 88th birthday, leaving behind films - most notably "Bonnie and Clyde" and "Little Big Man" - that refashioned movie and American history, made and broke myths and sealed a generation's affinity for outsiders.
Daughter Molly Penn said her father died at his home in Manhattan of congestive heart failure. A memorial service will be held by year's end, longtime friend and business manager Evan Bell said Wednesday.
Penn - younger brother of the photographer Irving Penn - first made his name on Broadway as director of the Tony Award-winning plays "The Miracle Worker" and "All the Way Home," then rose as a film director in the 1960s, his work inspired by the decade's political and social upheaval.
"Bonnie and Clyde," with its mix of humor and mayhem, encouraged moviegoers to sympathize with the marauding robbers, while "Little Big Man" told the tale of the conquest of the West with the Indians as the good guys.
"A society would be wise to pay attention to the people who do not belong if it wants to find out ... where it's failing," Penn said.
Penn's other films included his adaptation of "The Miracle Worker," featuring an Oscar-winning performance by Anne Bancroft; "The Missouri Breaks," an outlaw tale starring Marlon Brando and Jack Nicholson; "Night Moves," a Los Angeles thriller featuring Gene Hackman; and "Alice's Restaurant," based on the wry Arlo Guthrie song about his being turned down for the draft because he had once been fined for littering.
"I loved working with Arthur," said Hackman, who also worked with Penn on "Bonnie and Clyde" and the 1985 thriller "Target."
"He had his own clear vision, but he was really excited to see what you could bring to a scene, every take," Hackman said in a statement. "You could feel him over there, just by the camera, pulling for you. However rough and tough his films are, you can always sense his humanity in them."
Penn was most identified with "Bonnie and Clyde," although it wasn't a project he initiated or, at first, wanted to do. Warren Beatty, who earlier starred in Penn's "Mickey One" and produced "Bonnie and Clyde," had to persuade him to take on the film, inspired by the movies of the French New Wave. (Francois Truffaut and Jean-Luc Godard each turned down offers to direct the film.)
Penn, in his 40s when he made "Bonnie and Clyde," took full advantage of his gorgeous lead actors - Beatty and Faye Dunaway - and of the story, as liberal in its politics as it was with the facts - a celebration of individual freedom and an expose of the banks that had ruined farmers' lives.
Released in 1967, when opposition to the Vietnam War was spreading and movie censorship crumbling, "Bonnie and Clyde" was shaped by the frenzy of old silent comedies, the jarring rhythms of the French New Wave and the surge of youth and rebellion. The robbers' horrifying deaths, a shooting gallery that took four days to film and ran nearly a minute, only intensified the characters' appeal.
With the glibbest of promotional tag lines, "They're young ... they're in love ... and they kill people," it was a film that challenged and changed minds. Beatty worked for a reduced fee because the studio, Warner Bros.-Seven Arts, was convinced that "Bonnie and Clyde" would flop.
On Wednesday, Beatty fondly recalled working with Penn.
"I will always treasure the singularly honest, joyful, adventurous intelligence of Arthur Penn both as a collaborator and as a loving friend," Beatty said in an e-mailed statement.
"Bonnie and Clyde," released in August 1967 and then rereleased early in 1968 in response to unflagging interest, appalled the old and fascinated the young, widening a generational divide not only between audiences, but critics.
The New York Times' Bosley Crowther, then at the end of his career - an end hastened by "Bonnie and Clyde" - snorted that the film was "a cheap piece of bald-faced slapstick comedy that treats the hideous depredations of that sleazy, moronic pair as though they were as full of fun and frolic as the jazz-age cutups in 'Thoroughly Modern Millie."'
But Pauline Kael, just starting her long reign at The New Yorker, welcomed "Bonnie and Clyde" as a new and vital kind of movie - an opinion now widely shared - and asked, "How do you make a good movie in this country without being jumped on?"
"The accusation that the beauty of movie stars makes the anti-social acts of their characters dangerously attractive is the kind of contrived argument we get from people who are bothered by something and clutching at straws," Kael wrote. "'Bonnie and Clyde' brings into the almost frighteningly public world of movies things people have been feeling and saying and writing about."
The film was nominated for eight Academy Awards, with Estelle Parsons winning for best supporting actress, and is regarded by many as the dawn of a golden age in Hollywood, when the old studio system crumbled and performers and directors such as Penn, Beatty, Robert Altman and Martin Scorsese enjoyed creative control.
Penn, who had fought - and lost to - the studios over the editing of such early films as "The Left Handed Gun" and "The Chase," now was able to realize a long-desired project - an adaptation of "Little Big Man," based on the Thomas Berger novel.
"Originality is filtered out like tar is filtered out of cigarettes," Penn once complained. "I have not had a lot of success with the suits - or the dresses. Executives are executives. They're going to interfere as much as they can.
"('Little Big Man') didn't happen until I had so much clout I sort of made it happen."
None of Penn's other films had the impact of "Bonnie and Clyde," but the director regarded "Little Big Man," released in 1970, as his greatest success, with Dustin Hoffman playing the 121-year-old lone survivor of Custer's last stand. It was, again, a violent and romantic re-imagining of the past and an angry finger pointed at the war and racism of the present.
Penn earned Academy Award nominations for both films and for his first movie, "The Miracle Worker," based on the Broadway show about Helen Keller, played by Patty Duke in an Oscar-winning turn, and her teacher, Anne Sullivan, played by Bancroft. Among Penn's other stage credits: "All the Way Home," which won both the Tony and Pulitzer Prize in 1961 as best play; "Two for the Seesaw"; the musical version of "Golden Boy"; and "Wait Until Dark."
Penn traced his affinity for alienated heroes and heroines to the trauma of his childhood. Truffaut's film "The 400 Blows," he once said, "was so much like my own childhood it really stunned me."
When he was 3, Penn moved from Philadelphia to New York with his mother after his parents divorced. He and his mother, a nurse who had run a health food store, lived in a succession of apartments in New Jersey and New York City, and the boy attended at least a dozen elementary schools.
At age 14, Penn returned to Philadelphia to live with his ailing father and help him run his watch repairman's shop.
"He was an excellent mechanic. ... His hands were magical," Penn said. "But he was an evasive man for someone to try to make contact with. I think I'm like him in some ways. I'm not the most available of men, emotionally or personally."
He was no filmgoer as a child; books and baseball mattered more. Penn was frightened by a horror picture when he was 5 and said he did not see another movie until his teens, when Orson Welles' "Citizen Kane" "staggered" him.
Along with Welles and Charlie Chaplin, Penn greatly admired Akira Kurosawa and the French New Wave directors, especially Truffaut and Godard.
He was known for allowing actors to improvise - and getting a wide range of expression from them in return. He believed words are to the theater as action is to film: "A look, a simple look, will do it."
Penn's 1960s success was bracketed by frustration. Early in his career, he was so angered by how Warner Bros. changed "The Left Handed Gun," a Western released in 1958, that he stopped making movies and turned to Broadway. He was fired from "The Train," a 1964 film, over disagreements with the lead actor, Burt Lancaster. And none of his later works found favor at the box office, though several - "Night Moves" (1975), "The Missouri Breaks" (1976) and "Four Friends" (1981) - won critics' praise.
Penn decided to live in New York, rather than Los Angeles, as Hollywood soured on his social vision. Broadway, too, seemed increasingly drawn to blockbuster musicals rather than serious drama, further marginalizing Penn.
"It was frustrating and more than a little humiliating," Penn once told The New York Times.
"It's not that I've drifted away from film," he said in another interview. "I'm very drawn to film, but I'm not sure that film is drawn to me."
Arthur Hiller Penn was born in Philadelphia on Sept. 27, 1922, the son of Harry and Sonia Penn and brother of Irving Penn. Although both sons were involved in the visual arts, Arthur Penn later said that he saw little in common in their work and rarely discussed the ties between them. (Beatty would claim the director was influenced profoundly by his brother, who was known for a spare but dramatic photographic style. The older brother died in October 2009.)
Penn joined the Army during World War II, formed a dramatic troupe at Fort Jackson, S.C., was often in trouble for behaving disrespectfully to his superiors and was in an infantry unit that fought in the Battle of the Bulge. After the war, he studied literature in Italy for two years, then returned to New York, where he found work as a floor manager on NBC-TV's "Colgate Comedy Hour."
By the early 1950s, Penn was writing and directing TV dramas. In 1956, he debuted as a Broadway director, but "The Lovers" closed after just four days.
As a boy, Penn had little success learning the watchmaker's trade from his father, who died without having seen any of his son's films.
"He went to his grave despairing I would never find my way in the world," the director said, "and the movies rescued me."
AP Television Writer Frazier Moore and National Writer Hillel Italie contributed to this report.