The leopard strayed into Bairgachhi-Araria locality and attacked a child and a police constable Surendra Kumar Bharti and injured the two severely, Additional Superintendent of Police (ASP) Rajiv Ranjan said.
Soon, a mob gathered at the spot and an unidentified man shot at the animal killing it on the spot, Ranjan said.
Both the victims were taken to Sadar hospital for treatment, the ASP said adding, the cop had risked his own life to rescue the child from the leopard.