Johnson, 31, was taken to hospital after being knocked out by Paul Vaden in the 10th round of their United States Boxing Association junior middleweight title fight. He bled between his brain and his skull, with swelling on the left side of the brain.
Doctors drilled two holes in his skull to drain some fluid and relieve the pressure on his brain, but Johnson remained in critical condition, and was on a ventilator for two weeks, up until his death.
Johnson, who turned professional in 1987 and had a record of 27 victories, eight draws and one defeat, had suffered another head injury in a fight in Toronto on 14 April but on that occasion he was released from hospital within hours. Under Ontario boxing rules, he was automatically suspended from fighting or training for 60 days. But the ban did not extend to New Jersey.
Johnson won two fights after the Canadian ban and underwent a CAT scan to his brain before the Vaden fight. It showed no damage, according to his manager, Kenneth Woods.
Woods said that he urged Johnson to retire after that, but the fighter replied that he wanted to make more money so he could move his mother out of the New York housing projects. He was to receive $100,000 (pounds 64,000) to fight Vaden.
Johnson was leading on two of the three judges' score cards when Vaden knocked him out. Johnson's head struck the bottom rope in the ring before slamming on to the canvas.
"It's just devastating whenever this happens to anybody in the sport," Vaden's co-manager, Craig Hamilton, said . "It's a terrible thing for him, for his family, for the sport. I just wish we could find a way to avoid these situations."Reuse content