The FAA is saying it was an AugustaWestland 139, a large twin turbine helicopter used by many nations's military and coast guard units. It can seat two crew and up to 15 passengers in some configurations. Weighs about 15,000 pounds and costs about $14 million dollars. Still, no point in departing overwater at 2 am. With a mechanic on board you question if he had been sent over earlier to fix something and a maintenance delay was the reason for the late departure.