An army jawan shot dead his colleague and then killed himself in the Bihar capital on Monday after an altercation, police said.Both were jawans of the Bihar Regiment, an infantry regiment of the Indian Army. The Bihar Regiment centre is located in Danapur in Patna.Santosh Kumar Singh shot dead his colleague Rinkesh Kumar and then turned the gun on himself. Their bodies were found at a rented house in Manglam colony in Danapur in Patna, police said.Police have also recovered a sophisticated rifle from the incident site.Police have began investigation into the incident.Some residents informed police that the killing took place after a heated exchange of words between the two jawans over some issue. "Police will try to find out the exact dispute," a district police official said.