A husband-wife duo were killed on the spot and one of their sons succumbed to injuries during treatment after unidentified gunmen opened fire on the family at their home in Hathua area of Gopalganj on Sunday, police said.
Another son of the couple is undergoing treatment at a hospital in Gorakhpur, Uttar Pradesh.
DGP Bihar Gupteshwar Pandey said, "I got information and we are investigating."
( With inputs from ANI )