(NBC News) - A 16-year-old running in an annual mountain race in Alaska was fatally mauled by a bear on Sunday, according to local reports.

Authorities launched a search for the teen after he sent a text message to a relative saying he was being chased by the animal, according to the Alaska Dispatch News.

The 16-year-old was taking part in the Robert Spurr Memorial Hill Climb, which began at the Bird Ridge Trailhead southeast of Anchorage. He was making his way back down the mountain when he came across the black bear, the paper reported.

Troopers, the National Guard, park rangers and the Anchorage Police Department responded to the call, while other runners volunteered to search for the boy, according to NBC affiliate KTUU.

"I've been running in the mountains for 30 years," said Brad Precosky, a director of the race. "People come down off the trail and say they've run into a bear. Sometimes that means nothing; other times, it's really serious. Like this."

The teenager reportedly sent a text message to his mother during the race, sometime around 12:30, saying he was being chased by a bear. 

"The mother was here with her family, her children," said Anchorage Police Dept. Sgt. Nathan Mitchell. "They were running the race."

Precosky said the teen's fellow competitors had lost him in thick brush. When one came barreling down the trail saying there had been an attack, he said, the entire race crew went into crisis mode. 

Other runners, most of whom who had completed the race already, immediately volunteered to be part of the search for the boy. They returned - weaponless - to the trail.

"There were probably a dozen mountain runners up there keeping the bear on its toes," Precosky said.

One of the runners said he saw a bear circling the teen somewhere off the beaten path.

John Weddleton, who didn't win a lottery spot for the race this year but attended to cheer his fellow runners on, was first to find the boy after the attack. 

"I ran up to cheer, came down, and thought, I might as well go back up," he said. "All I knew was there was a boy missing, and missing in bear country."

The teen was eventually found off the main trail. He was pronounced dead at the scene.

A Chugach State Park ranger shot the bear, but it ran away. Rangers and the Alaska Department of Fish and Game are still looking for the animal, according to the paper.