1. A two-minute shot per month in the duration of 15 years = 360 minutes (15 days' worth of footage), which is way more than enough to fill a hour-and-half film. Since they are film-makers, they would have a lot more footage than that.
2. They did talk to him. How else did they know how he felt and experienced? And what prompted them to seek professional help to help him?
3. Hindsight and all that. I'm pretty certain that after he died, they looked at archival footage and noted the significance of his actions. They edited those into their documentary. I bet that when they filmed him at the time, they just took it for granted that it was just part of growing up.
That's part of the pain they have to deal with, just like all other parents who went through the same thing. "Why didn't I spot it? Why didn't I realize the significance of what he did when I thought he was just having fun?" So yeah, give them a break.
4. My great-uncle filmed my great-grandfather's funeral with a Super 8 camera during the 1970s. :D He did it for those who couldn't make it to the funeral.
this wasn't hindsight. this kid pretty clearly had a screw loose and the parents seemed like they weren't doing enough to help. plus the whole thing felt very manipulative.
i told you not to stop the boat. Now lets go. Apocaylpse Now