Not meant to be offensive, just my opinion based on what you portray to be your opinion/beliefs in this thread.
Ie. it's ok to drink and drive provided it's not by too much (about 30% over the limit in your example). Doesn't matter how over the limit someone is they are deemed not capable of driving, that translates to not safe, a danger to themselves and others, etc etc. But no, according to you it would just be a 'mistake' when said drink driver kills another person be that another driver/occupant of car/pedestrian and a quick pat on the back or a bit of a hug and all we be well, just sleep it off and carry on again tomorrow as everyone makes mistakes now and then, right.
What was the drivers mistake here, driving at over 60mph in a 30mph zone? failing to brake? crashing before he could get away (hit and run maybe)? not paying enough attention to what was happening around/ahead of him?
The decision he made to drive double the limit was not a mistake, he chose to do that. Also appears he chose to try and keep on driving away from the scene before he crashed further down the road.
Did he know the risk of driving at that speed in a built up area, can't be sure that he did but ignorance is no defence.
Perhaps you'll appreciate the risks others take with your children more if you ever have your own and at that point your opinion may change.