Raj Kumar Singh Yadav (52), along with another constable Rajendra Prasad, had gone to Budhaura village under Raniganj Kotwali police station area in connection with investigation in a case, a senior police official said.
There the constables entered into a heated exchange with Irshad, a notorious criminal, assistant superintendent of police Swami Nath said.
As the argument intensified Irshad opened fire at Yadav, who was rushed to a hospital where the doctors declared him dead, the ASP said.