What's the example Chris' dad gives of how fearless Chris was?

Chris wanted to climb to the top of the summit at Longs Peak in Colorado, even after his father decided to turn back.

"... Chris wanted to keep going to the top. I told him no way. He was only twelve then, so all he could do was complain. If he’d been fourteen or fifteen, he would have simply gone on without me.” Walt grows quiet, staring absently into the distance. “Chris was fearless even when he was little,” he says after a long pause. “He didn’t think the odds applied to him. We were always trying to pull him back from the edge.”