Hundreds gather in front of a house in Thanh Hoa Province where locals discovered dead bodies of four family members on Sunday night. Photo: Hoang Le/ VnExpress.
Police in Thanh Hoa Province said a man might have drugged and killed his family with sleeping pills before committing suicide on Sunday.
Investigators said they also found a suicide note and a recording apparently left by Ngo Le Ha, 55.
They said the evidence showed that he hanged himself after his wife and their two sons, aged 23 and 13, died. It is not immediately clear how the three were drugged or if they knew about his plan.
Police said the family was struggling with unpaid debts.
Their bodies were found at home on Sunday evening, after many friends and relatives of the family had failed to contact them for hours.
Ha and his wife ran an electronics shop at the first floor of their house.
Some of their employees said they came for work on Sunday morning and found the shop closed.
The employees told police that they thought their boss had left for some business and closed the shop for one day.