Very sad.
The pics of the accident tell me that the guy behind the wheel had no idea where he was going. And as bad as the boat flipped, 30mph+ would be a good guess.
When boating at night:
1. Know where one is at all times. If unsure, get out in the water during the day to visually check it out. A GPS unit as low as $150 would have probably saved his life.
2. Have plenty of lights. The more the merrier. Don't forget flares.
3. Speed is a killer at night. Slow down. And don't drink and navigate a boat at the same time.