Bodies of constable Rinkesh Kumar Singh (22) and Lance Naik Santosh Kumar Singh (35) were found from a house at Judges colony in Danapur area.
Santosh's service rifle was used in the killings.
Rinkesh was posted as a clerk in Danapur Army cantonment while Santosh was posted in Arunachal Pradesh, Assistant Superintendent of Police Rajesh Kumar said.
Santosh was on leave and Rinkesh had left Danapur cantonment yesterday afternoon.
The two were good friends and Santosh wanted Rinkesh to marry a relative of his but the latter was reluctant, Kumar said.
Without getting any reply from inside, Rinkesh's brother-in-law with the help of Santosh's landlord broke open the door and found their bodies bearing bullet wounds, the police officer said.
A forensic team has collected samples from the spot.