The crank snapped on the drive side crank arm pedal eye while he was standing on the pedals. He's got a short ride and likes to go fast.
From the dark spot on the cracked surface in the attached photo, its obvious that the crack started much earlier than the break. Close inspection would have prevented the accident. But my son is not a bike rider, he's a commuter ... he bought the bike new hoping that it would be trouble-free for years to come. (I should mention that he bought it new after many years of riding old fixer-uppers that I gave him). This problem may be a fluke but it should never happen on a new (1 year old) bike !