To sum it up, with one motherhood statement "Multiple factors contributed to the fatalities" If the driver had been more careful, if the boys had been more careful, if the parents had been more careful, if the govt has been more careful... etc... any of these IFs could have saved the boys.
As a driver, i constantly remind myself, no matter how much i enjoy treating the road like a race circuit... have some regards for life. That means anywhere near junctions, filters, unbarricaded roads, anywhere that could potentially have a human traffic => drive with care.
IN this instance, if the kids are killed in that manner, i am SURE the truck was not moving from standstill. It definitely came from far at high speed. So even if the kids contribute to their own death... the driver deserve to spend the rest of his life regretting his actions.