Sitamarhi (Sadar) Deputy Superintendent of Police M N Upadhyaya said the incident happened when Sanjay Kumar Mahto was on a morning walk.
"Two criminals on a motorcycle accosted him and fired from a pistol. Mahto was hit and fell on the ground. The attackers then fled," Upadhyaya said.
The victim was taken to a private hospital where his condition was stated to be critical.
"We are not certain about the motive behind the attack, but two attackers have been identified. Raids are on to arrest them," the DSP said.