It was a decision that changed his life.
After years of fighting on the streets, Johnson redirected his energy to fighting in a boxing ring.
Today, as manager and coach of the Hagerstown Boxing Club, he sees himself in some of the young men who walk into his gym.
"I came from hard knocks," he said. "But boxing can bring a purpose to your life."
Johnson said he was introduced to the sport by his uncle, a Philadelphia boxer who fought some of the top fighters of his time, including Rocky Marciano.
"My grandfather asked him to take me to a gym to learn boxing," the Hagerstown resident said. "So he took me to a place on Columbia Avenue, a gym where a lot of famous boxers trained. Boxers like Joe Frazier, Hal Johnson and Bobby 'Boogaloo' Watts."
Within a few days, Johnson was getting into shape and learning the basics of boxing - how to stand, how to hold his hands and how to move his feet. He was shadow boxing and learning offense and defense.
"And I began to like it," he said. "I was fighting, but this time I had gloves, a mouthpiece and headgear."
Johnson said he did pretty well, winning his first fight at the age of 13 and eventually winning the district Golden Gloves and advancing to the nationals.
"Boxing was now in my blood," he said.
After high school, Johnson volunteered for the Army, where he boxed on a military team, had 25 fights and was undefeated.
After leaving the Army, and at the urging of several scouts, Johnson turned pro as a welterweight.
"I stayed with it for five years," he said. "But I couldn't get many main event fights, wasn't making much money and began to get discouraged. When my contract was up, I decided to split."
Johnson then became a probation officer in Philadelphia.
But boxing never was far from his thoughts.
"Once you get a taste of boxing, it's with you forever," Johnson said. "I knew I'd be involved with boxing again at some point in my life."
In 1969, he accepted a position with the U.S Forest Service and National Park Service as part of the Job Corps program, working with disadvantaged youth in Virginia and, later, in Kentucky, North Carolina and West Virginia.
"I loved it," he said. "I loved seeing these young people get an education and get motivated."
Johnson stayed until 1975, when he began to get the itch to return to boxing - this time as a trainer. He headed to Washington, D.C., where he landed a job at Finley's Gym, working with amateur and professional fighters, including Vincent Thompson and David Izegwire.
That year, he met Dick Hess, who taught boxing at the Boys & Girls Club in Hagerstown. They became best friends, with Johnson counseling some of Hess' fighters.
Tired of city life, Johnson decided to move to Hagerstown in the late 1980s "to escape the rat race and congestion."
That's when Hess introduced him to Bob Strout, president of Has Beens Boxing Club in Cumberland, Md., who asked him to join his group as a trainer. Five days a week, Johnson traveled to Cumberland, working with amateur fighters. When Strout became ill, he entrusted Johnson with the boxing ring he had purchased. In 1995, following Strout's death, Johnson and Hess moved the ring to Hagerstown.
Since that time, the renamed Hagerstown Boxing Club has been at several locations. Today, the gym has a home at 245 Prospect Ave.
Johnson said many people pass by the gym every day and don't realize it's there.
"People know about us by word of mouth," he said.
About 20 young people, amateurs and professionals, between the ages of 8 and 25, train at the club, Johnson said.
"There's a high level of dedication," he said. "Some of the guys will be here five days a week, several times a day, working out and practicing for weekend bouts. The more time you put in, the better you get. Some people see how much work is involved and drop out. You have to really want it to be part of this. There is no season in boxing. You train year-round."
While some people may think boxing is a violent sport, Johnson considers it an art.
"It takes skill to be a fighter," he said.
Johnson also said the sport is safer than when he was a boxer.