Police say boxer Paul Williams was driving his modified sport motorcycle too fast for conditions when he crashed into an embankment.
His manager, George Peterson, said the boxer was paralyzed and has no movement from the waist down after Sunday's crash in Marietta, northwest of Atlanta.
Peterson said the 30-year-old athlete severed his spinal cord after falling on his back and head when he was thrown from his motorcycle.
Marietta police said in a statement Tuesday morning that Williams was driving at a high rate of speed which was too fast for conditions. Police say he could not negotiate a curve, and the bike slammed into the embankment.
Peterson said Williams was scheduled to fight Saul "Canelo" Alvarez on Sept. 15 in Las Vegas but that event has been canceled.