Bell, 32, was booked Sunday on suspicion of assault with a deadly weapon, according to a statement by the San Bernardino County sheriff's department.
A telephone listing for Bell was disconnected. He did not immediately respond to an e-mail seeking comment.
Deputies responding to a possible fight off Highway 38 found Bell's sparring partner, 37-year-old Larry Slayton, afraid for his life with cuts from running through the brush, sheriff's spokeswoman Arden Wiltshire said Monday.
Slayton told the deputies Bell had become angry with him during a training session in the woods and threw a hatchet the boxer was carrying for protection against bears. Slayton fled, dodging large rocks Bell threw at him, Wiltshire said.
Bell posted $50,000 bail. Wiltshire did not know whether an arraignment date had been scheduled or if Bell had retained a lawyer.
Bell (26-1-1) was in Big Bear training for a March 17 rematch title fight with Jean-Marc Mormeck in Paris.
Bell defeated Mormeck in January 2006, making him the first undisputed champ in that weight class since Evander Holyfield in 1988. The Jamaican has since lost his IBF title through inactivity.
Big Bear, a popular spot for fighters to train, is located about 90 miles east of downtown Los Angeles in the San Bernardino Mountains.