The three assailants brandishing firearms attacked RSS worker Rajesh Mishra, 40, who is also a journalist, when he and his brother were sitting in their building material shop in Brahmanpura Chatti, circle officer Hridayanad Singh said.
Mishra was shot in his head.
When his brother Amitesh Mishra, 35, intervened, he was shot in the abdomen, Singh said.
The brothers were taken to the district hospital, where Rajesh was declared brought dead, while Amitesh was referred to Varanasi for treatment.
ADG Law and Order Anand Kumar said in Lucknow that two of the attackers have been identified.
"Of the three assailants, two have been identified, and soon all of of them will be arrested," he added.
Image used for representational purposes only. Photograph: PTI Photo