Forty-five years ago Saturday, he took what is probably the most famous home movie in history . Almost anyone who was alive on Nov. 22, 1963, remembers exactly where he or she was when first hearing about the event his film captured in such grisly detail.

Yet today Abraham Zapruder has returned to the obscurity from which he was catapulted with six seconds of 8 mm film documenting from start to bloody finish the assassination of President John F. Kennedy.

On the anniversary of that tragedy, the ferocious debate over who shot the president and why shows few signs of abating. So it is interesting to consider the Dallas businessman, then 58, who in many ways is responsible for igniting the controversy over the possibility of a plot to murder the president. Without the Zapruder film, the conspiracy theorists would have precious little to work with.

He was born in Russia, educated at a Hebrew school and came to New York with his mother and sister when he was a teenager. His father had preceded them. A brother started the trip but, as Zapruder described it much later, was pulled off the train and killed by anti-Jewish thugs. Zapruder says he was spared himself because he had blond hair.

He landed a job in the garment district as a pattern cutter, worked up to head of crew and was lured to Dallas in 1941 as production chief of a dress factory there. With a partner, he ultimately started his own line, Jennifer Juniors, the name borrowed from the movie star, Jennifer Jones.

It was a thriving business, $2 million gross, and Mr. Z, as everyone called him, was a stern but popular boss. On most work days, he and Erwin Schwartz, the son of his original partner, wandered over to Sanger's Department Store in the afternoon for a banana split or ice cream soda. Mr. Z rarely got mad, but when he did — at Erwin or a worker or a salesman — he would walk across the street and sit on a park bench until he cooled down.

Zapruder was perhaps 5 feet, 9 inches, a trifle plump, bespectacled, balding and a fastidious dresser who favored white shirts and bow ties. A sociable man, he loved telling stories, sometimes in a Jewish dialect that would be considered politically incorrect today — tales about Russia, New York, business, whatever, while he puffed on a cigar (and drank sparingly). Schwartz suspected that his partner may have made up some of the stories, "but I enjoyed them and I believed them."

Late in life, Zapruder took up golf, and he and Schwartz waged putting contests on the office rug. At stake was a $1 bet. Zapruder played the piano fairly well, mostly light classics, and sang, as his lawyer Sam Passman recalled, "badly." He and his wife, Lillian, had a son and a daughter, and Zapruder loved to shoot home movies of them and later on, of his grandchildren, his friends, his employees. He was a real 8 mm buff.

It was natural, then, for him to take his camera to nearby Dealy Plaza that November morning for a memento of the president he had voted for, and greatly admired as someone who "had gotten the country on the right track."

That day changed him forever, his friends say. "Just remember that we've only seen the film," one of them pointed out. "He saw the actual murder." For a while Zapruder had nightmares, jerking awake when his sleeping eye came upon frame 313, the tiny speck of film that records the horrifying head wound. He wept while testifying before the Warren Commission that investigated the assassination. "I'm sorry," he told the commission. "I'm ashamed of myself really, but I couldn't help it." His wife, Lillian, acknowledged, "He was extremely emotional about the whole thing."

He became an unwilling celebrity. As many as 10 sacks of mail arrived daily, addressed simply to "Abraham Zapruder, Dallas, Texas." Some letters called him a fool for contributing $25,000 to the family of the Dallas police officer killed by Lee Harvey Oswald. That amount was the first of six annual payments from LIFE Magazine, which had bought the film the day after the assassination (and in 1975 returned it to the Zapruder family for $1). When he and his wife traveled, the Zapruder name was sometimes recognized on hotel registers. He hated the notoriety.

He had little use for the army of conspiracy theorists the assassination spawned. After agreeing to see an early conspiracy author, Mark Lane, who wrote Rush to Judgment, one of the first anti-Warren Report books, Zapruder got so upset over Lane's questions that he asked the writer to leave his office. Until Zapruder's death from cancer in 1970, he believed, as did the Warren Report, that Kennedy was murdered by "a crackpot, a nut" — in short by Oswald acting alone.

Although a shrewd businessman, he recoiled from being seen as profiting from the president's death. He asked LIFE to keep the amount it paid him confidential. In 1999, his name was splashed on front pages again when the federal government agreed to pay his family $16 million for possession of the fragile piece of film. It is fair to speculate on how Zapruder himself might have reacted to such a payoff.

In return for a new camera, Zapruder gave his historic camera to Bell & Howell, which donated it to the National Archives. But he rarely used the new one in the final years of his life. Mr. Z's enthusiasm for home movies ended on Nov. 22, 1963.

Richard B. Stolley, senior editorial adviser at Time Inc., was the LIFE reporter who obtained the Zapruder film for his magazine in 1963, 45 years ago today. He now lives in Santa Fe with his wife, Lise Hilboldt, and son.