I knew Mark briefly in the mid-1970s, as my parents lived in Manchester, New Hampshire, where Mark was still in high school. I was just back from my first post-college climbing trip, having spent several months in the Canadian Rockies. I spent a winter living with my parents, working at my uncle's store, and cragging at Manchester's scruffy Rock Rimmon. I did some modest routes with him and his pals, all rock climbing well above my grade, however I fared a little better on ice. Mark cruised out to the valley and became the youngest person (16 years old) at the time to climb El Cap.
An excellent video, as this unlikely duo try and free climb El Cap.
https://vimeo.com/449058597