A retired school teacher, Laxmi Narayan Mahto, 70, was shot dead around 6am on Sunday.
The incident occurred after he came out of his residence at Daroga Tola area in Motihari. Mahto was rushed to Dr Rahmania Medical Centre, where he succumbed to his injuries.
Witnesses said about six bike-borne criminals, who had covered their faces, shot at Mahto from point-blank range after a brief altercation with him.
Deputy superintendent of police (sadar) Sushant Kumar Saroj said the police apprehend that a land dispute might have led to the murder.