Radhey Yadav, a resident of Seer Kirheya had come to Kotwalpura along with two others Suresh and Arvind to attend a party organised by their relative Bablu.
According to the Additional Superintendent of Police, Santosh Singh an altercation broke out between Radhey and Suresh at the party, following which the latter left.
After sometime, Suresh returned to the spot on a bike and took Radhey behind the house where he allegedly shot him in the head and fled, police said.
The incident took place within the Yellow Zone (middle security cordon) of the highly-sensitive Kashi Vishwanath Temple complex, manned by security forces especially after the December 2010 blast.
Police detained Arvind, who under the influence of alcohol, could not reveal anything during interrogation.
They have launched a manhunt to nab Suresh.