The incident occurred in the early hours when the Army personnel, a resident of Rohtas district, was returning home from a marriage function.
The attackers, four to five in number, surrounded him and tried to loot his belongings, and one of them fired at him when he resisted, Deputy Inspector General of Central Range (Patna) Rajesh Kumar said.
The man received a bullet injury in the neck and is stated to be in critical condition, the police officer said.
The SHO of Gandhi Maidan police station, Mitesh Kumar, has been suspended since the incident took place under the jurisdiction of his police station, the DIG said.
The DIG also said that he has suspended four other policemen who were on patrolling duty at Gandhi Maidan police station area for dereliction of duty.