The two climbers had been careful. They planned their route. They were well-anchored. They wore helmets.

But they hadn't counted on every climber's worst nightmare, a 15-to-20-pound rock that came hurtling down at them after being tossed from above by a hiker who said he didn't see them.

The rock hit Peter Absolon, the 47-year-old regional director of the National Outdoor Leadership School in Lander, Wyo.

Friends were stunned when they heard Absolon was dead and dismayed when they learned how he had died while climbing the Leg Lake Cirque in the Wind River mountain range Saturday.

"Pete was a solid guy. The word I like to use is unflappable," said Phil Powers, executive director of the American Alpine Club in Golden and a longtime friend and climbing partner of Absolon's.

Most climbing accidents involve some degree of human error, Powers said.

So when he heard that Absolon had been killed, he was "astounded." Absolon was just such a consummate, careful climber and not prone to make mistakes, he said.

But as it turned out, Absolon and his partner were doing everything right.

"And then this unfortunate coincidence and senseless act combined to cause his death," he said.

Fremont County Attorney Ed Newell II has said he wants to talk to Absolon's family and friends before deciding whether charges should be filed against the 23- year-old man who tossed the rock.

Authorities have declined to identify the man, but Newell described him as remorseful and cooperative with investigators. He told them he did not see Absolon when he tossed the rock.

Among climbers, there is a widely held understanding never to toss rocks or any objects off the side of a mountain, said Gary Neptune, of Neptune Mountaineering in Boulder. Even a pebble can start a rock slide or cause serious harm, he said. When it happens by accident, they shout "rock" to anyone who might be climbing below.

The area where Absolon was climbing with a friend was a rock cliff visible from Lander.

They were on a route that no one had ever attempted before, said Gary Wilmot, an instructor and development officer at NOLS.

"It was going amazingly well. He and his partner were having a fabulous day in the mountains," Wilmot said.

"The blessing is that he was in a place and in a moment when he was happy."

Absolon and his wife, Molly, have a daughter, Avery, who turns 7 next month.

ensslinj@RockyMountainNews.com or 303-954-5291. The Associated Press contributed to this report.