IMO, without knowing all the facts, it seems like it was simply an unfortunate accident.

While I do agree children should be exposed to proper firearm use and safety from an early age, one also has to keep in mind they are dangerous and sometimes stuff can happen. It's no different than teaching your kid to swim, teaching them to ride a dirtbike, or anything else like that. Sometimes you think you're doing everything right and still, something bad can happen.