Marah Strauch tells HuffPostUK that she deliberately left this part of the film unclear, as that was how investigations into Carl’s death panned out in real life.
"I decided not to lie about his end. There was no clear answer as to why he died, and a lot of people find that challenging," she says. "But that’s the truth. I could have manufactured something.
"There was no clear answer and if I’d tried to create one, I wouldn’t have been truthful.
“There is some beautiful drama to both the happy moments and sad moments. I really wanted them both to be there.
“He died as he lived and I wanted to show that visually.”
The documentary includes interviews with Carl’s widow Jean, and Marah defends her decision not to pry too forensically into the tragic events of July 1984, when Boenish died in a BASE jump off the Troll Wall in Norway, the day after completing a successful double BASE jump alongside his wife for a 'Guinness World Records' television special.
“We were very conversational. Some articles say that I’m not an investigative reporter, but I wouldn’t claim to be,” tells HuffPostUK. “I would say I’m a poet. I didn’t want to investigate, I wanted to observe. I could have been manipulative and made Jean cry, but I wanted her to tell me what she wanted to tell me.
“That was my desire, and that was what I wanted for Jean. I didn’t want to poke and pry. We had a nice rapport and it was important for me that she liked the film.”
This is the first feature film for Marah, who discovered Carl’s story among reels and reels of sky jumping footage in the basement of her late uncle, a cinematographer and another base jumping enthusiast.
“It took me eight years in total,” she remembers. “A lot of that time was spent saving up the money, and getting 200,000 feet of film transferred onto formats we could actually see. It wasn’t synched up with sound either. So it was like an enormous jigsaw puzzle.
“I didn’t know the story I wanted to tell, but I wanted to include the love story between Carl and Jean. So it was a case of hunting down that material. Carl was great at shooting BASE jumping, but he wasn’t good at filming his more personal moments.”
Sharing the beauty of Carl’s adventures as well as speaking to those left behind in their tragic aftermath, Marah has come to her own conclusions about the value of BASE jumping.
“I’m not so much of an athlete, but I really enjoy the beauty of people doing these things,” she says now.
“I don’t think BASE jumping is worth it for everybody, but it can give great lessons to those that don’t. I see great value in living your life authentically, the beauty of the fact that people can BASE jump, to be in a world where people do that.
“It also challenges notions of what’s impossible. People will ask, why do that? Well, because you can.”
'Sunshine Superman' is out on DVD and digital download from 28 September.