A climber who was descending Mount Hood in Oregon fell 500 feet to his death this weekend. 

The 63-year-old, whose name was not shared by authorities, was climbing the mountain with his adult son on Sunday during “an unusually busy weekend for climbing” at the volcano when he fell from an elevation of 10,500 feet around 9 a.m., the Clackamas County Sheriff’s Office shares.

The department set up a search-and-rescue team after witnesses called 911, the New York Post reports. The Portland Mountain Rescue and the Hood River Crag Rats search-and-rescue team pitched in to help with the search. 

Those searching for the man navigated “hazards posed by hydrogen sulfide and other toxic gases venting from fumaroles” and eventually found him motionless at 10:30 a.m., authorities shared.

It remains unclear what caused the man’s fall. He was pronounced dead at the scene and taken to a command post. 

“Warm weather at this time of year can create very unstable conditions on this area of Mt. Hood, including falling ice. The addition of many climbers of varying skill levels can add additional hazards,” Portland Mountain Rescue said in a statement, warning of climbing in the coming months. “Exercise caution while climbing Mt. Hood this weekend.”