A young male 35 years age was operated for Cholelithiasis (Lap. Cholecystectomy) cystic duct and artery cliped separetly and operation was uneventfull, after 12 hours patient take meal after that there was sudden haemorrhagic collection in drain (about 1200ml), patient was expired even after intensive effort, (patient preoperative investigation and history was WNL).

what was the cause ?.