Treadwell, 46, of Malibu, Calif., and his girlfriend, Amie Huguenard, 37, were killed in October 2003 by a bear in Katmai National Park and Preserve.

Treadwell was an author and videographer who devoted himself to saving grizzlies after he said he had near-fatal experiences with illegal drugs. He said close encounters with bears inspired him to give up drugs, study bears and work for their protection.

Authorities believe Treadwell and Huguenard were killed by a 1,000-pound adult male grizzly. An audio recording of the attack was captured by Treadwell's video camera.

The deaths were detected by a pilot who arrived to pick them up and saw a large grizzly standing over human remains.