National Track & Field Hall of Famer William "Parry" O'Brien, a two-time Olympic gold medalist in the shot put, died Saturday of a heart attack while competing in a masters swimming competition. He was 75.

The Olympic champion in the shot in 1952 and 1956, O'Brien was the silver medalist in 1960 and was flag bearer for the U.S. Olympic Team in 1964, when he finished fourth. He was the first man to break 60 feet in the shot, accomplishing it on May 8, 1954 - two days after Roger Bannister ran the first sub-4-minute mile.

O'Brien broke the world record in his specialty event 16 times, won 17 national shot titles outdoors and won an astounding 116 straight competitions in the 1950s. He won nine straight national indoor titles, as well as one championship in the discus outdoors.

Parry O'Brien revolutionized the shot put, making the "O'Brien Style" (or "O'Brien Glide") the accepted way to throw the 16-pound ball. His method of facing the back of the circle and using a 180-degree turn to shift the weight to the front of the circle made him the dominant thrower of his era.

O'Brien was the Pan-American Games champion in 1955 and 1959. He received the 1959 Sullivan Award as the nation's top amateur athlete. He later enjoyed successful careers in commercial banking, real estate and civil engineering. He began throwing again in the 1980s and set world age-group records in the shot and discus. He was elected to the U.S. Olympic Hall of Fame in 1984.

O'Brien's wife, Terri, reported that he began swimming in the 1990s. He died Saturday while competing in a 500-yard freestyle race in Santa Clarita, Calif. O'Brien lived in Rancho Belago, Calif. Survivors include his wife, two daughters, two stepsons and seven grandchildren.

For a bio of Parry O'Brien, click here.