BILLINGS, Mont. (AP) — Investigators say the killing of a Montana man by a grizzly bear underscores the need for hikers around Yellowstone National Park to travel in groups and take other precautions against bear attacks.

The U.S. Fish and Wildlife Service on Wednesday released a review board's report on the Aug. 6 fatal mauling of Lance Crosby. The 63-year-old Billings man was the sixth person killed by a grizzly since 2010 in the Yellowstone region of Wyoming, Montana and Idaho. Five victims were hikers, including four who were alone.

None of the hikers carried bear spray, a Mace-like device that can stop a charging bear. Roughly 700 to 1,000 grizzlies live in and around Yellowstone. State officials want to allow hunts of the federally protected animals partly to address conflicts with people.