Key points from linked article:
Aircraft departed KSTS at 0820L. Aircraft turned around at 1040L, reporting a fuel transfer system malfunction.
Pilots issued a distress call about 70 nm west of land that aircraft “was nearly out of fuel” indicating intention to ditch.
USCG spotted aircraft in water, upside down. Rescue swimmer noted both pilots still strapped into cockpit seats and unresponsive.
2 pilots killed on Hawaii-bound plane