A rescue mission Friday has become a recovery mission near the town of Index.

Snohomish County Sheriff's Office says a 21-year-old man was killed when a boulder fell on him.

The man was hiking with three other people near Heybrook Lookout Trailhead. He was climbing on a steep rock field when the boulder gave way, pinning him underneath.

The other hikers were able to call 911 while on the trail.

Crews with the Snohomish County Technical Rescue Team were able to access the hikers and bring equipment using a Polaris Ranger 6x6 and four-wheel drive vehicles. Teams set up a cable tension system to pull the boulder off the victim. Unfortunately, the hiker died from his injuries before crews arrived.

The sheriff's office says this is the second accident like this, this year. Due to the long, wet winter, the ground under the rocks are unstable. They're urging hikers to stay on the trails, not climb rock fields and always hike in a group.