At least three robbers broke into the two storied house locked their teenaged son in his room from outside.
When the constable, Rama Prasad Chandra, resisted their attempt, they stabbed him in his stomach, police said.
After they left, the constable's wife Jayanti, who is in another room and also injured by the robbers, rang up the neighbours and the couple's son.
When the police constable was taken to hospital he was declared brought dead.
His wife too later succumbed to her injuries, police said.