A hiker was killed by a grizzly bear in the the US Yellowstone National Park on Wednesday after he and his wife surprised the bear and her cubs on a popular trail, park officials said. The woman was not wounded in the attack. This was the first such killing in the park in nearly 25 years, the officials said. Grizzly bears can weigh up to 1,500 pounds (680 kilograms) and sport large shoulder humps. Despite their size, they can run up to 35 miles (55 kilometers) per hour, according to the US Fish and Wildlife Service. The bears tend to avoid humans, but can be extremely aggressive if they perceive a threat to their young. There are warning signs about grizzlies throughout the national park, and the attack took place in an area where bear-sightings are common. The last fatal grizzly attack in Yellowstone was in October 1986, when the mauled body of a man was found by the road near a camera and tripod, leading park officials to conclude he was killed while photographing the animals. Grizzlies used to range widely across the Rocky Mountains and the Great Plains, but hunting drastically reduced their numbers. Today they are a protected species found only in scattered locations, mainly national parks.