Sarairanjan police station SHO Manoj Kumar Singh said that the deceased has been identified as Dipu Kumar (12), a resident of Harpur Aloth village under Musrigharari police station of the district.
The incident occurred when a family was going to attend a marriage function in an autorickshaw at Bhagwatpur village from their native village Harpur Aloth in the district, he said.
The six injured of the family were admitted to a nearby private clinic. Three of them were referred to Samastipur Sadar Hospital later.