First, and quite obviously, I'm not an expert... just a Private Pilot with some experience with the conditions that day.
The flight began under legally acceptable conditions... but conditions deteriorated and apparently did so quite rapidly.
It's looking more and more like Pilot error... but we'll see.
Did a little research with the 'few' facts available and it sure seems like the end was sudden, with little to no warning. What I'm getting at is.... it's possible the pilot and passengers were unaware of the situation until right before the crash took place... or even NEVER aware.
It troubles me most regarding the 3 young girls who lost their lives so early in life. Obviously all the deaths are tragic... but I think even more tragic when it happens to those who are very young.