Kartikeya, who was arrested from Faridabad on Wednesday, was being brought to Kanpur
on transit remand when he snatched the pistol of a policeman and tried to flee, ADG, Law and Order Prashant Kumar said.
"The encounter took place in the Panki area of Kanpur when a police team was bringing Kartikeya alias Prabhat to Kanpur from Faridabad on transit remand. The police vehicle had a flat tyre. Taking advantage of the situation, Kartikeya tried to flee after snatching the pistol of a policeman," he said.
Kartikeya opened fire at the policemen accompanying him, injuring two Special Task Force (STF) personnel, and was killed in the ensuing exchange of fire, the officer said. The policemen fired at him "in self-defence", he added.
Kartikeya was rushed to the hospital, where he was declared dead by the doctors, the ADG said. Kartikeya, Ankur and Shravan were arrested following a late-night encounter in Faridabad on Wednesday.
Five persons have so far been killed in separate police encounters since the Kanpur ambush.
Earlier, Amar Dubey was killed in Uttar Pradesh's Hamirpur on Wednesday, while Prem Prakash Pandey and Atul Dubey were gunned down in an encounter in Kanpur on July 3.