Answer by taking a quote from the following article:

Robert Lee "Bullet Bob" Hayes (December 20, 1942 - September 18, 2002) was an Olympic sprinter turned American football wide receiver in the National Football League for the Dallas Cowboys. An American track and field athlete, he was a two-sport stand-out in college in both track and football at Florida A&M University. He has one of the top 100 meter times by NFL players. Hayes was enshrined in the Dallas Cowboys Ring of Honor in 2001 and was selected for induction in the Pro Football Hall of Fame in January 2009.

Hayes was a highly recruited athlete, and accepted a football scholarship from Florida A&M University a historically black college, where he excelled in track & field.  He never lost a race in the 100 yard or 100 meter competitions, but mainstream schools of the area still did not invite him to their sanctioned meets. In 1962 the University of Miami invited him to a meet on their campus, where he tied the world record of 9.2 seconds in the 100-yard dash, which had been set by Frank Budd of Villanova University the previous year. He also was the first person to break six seconds in the 60 yard dash with his indoor world record of 5.9 seconds.  In 1963, although he never used a traditional sprinter form, he broke the 100-yard dash record with a time of 9.1, a mark that would not be broken for eleven years (until Ivory Crockett ran a 9.0 in 1974). That same year, Hayes set the world best for 200 meters (20.5 seconds, although the time was never ratified) and ran the 220 yard dash in a time of 20.6 seconds (while running into an eight mph wind). He was selected to represent the United States in the 1964 Summer Olympics in Tokyo. His football coach Jake Gaither was not very high on giving Hayes time to train, which caused then president Lyndon B. Johnson to call him in order to allow Hayes time off and to keep him healthy.  He was the AAU 100 yard dash champion three years running, from 1962-1964, and in 1964 was the NCAA champion in the 200 meter dash. He missed part of his senior year because of his Olympic bid for the Gold medal.  In 1976, he was inducted into the inaugural class of the Florida A&M University Sports Hall of Fame. In 1996, he was inducted into the Southern Intercollegiate Athletic Conference Hall of Fame. In 2011, he was inducted into the Black College Football Hall of Fame.

When did his college career end?
He was selected to represent the United States in the 1964 Summer Olympics in Tokyo.