A passerby suffered a gunshot injury in the Sunday night incident. It took place near Balak Baba Mathia on the Lalganj-Gopalpur road, the police said.
Sumer Singh was on his way to a pre-wedding function along with his friend Chunnu Misra when the assailants shot him in the head. The injured passerby was identified as Bhutaili Yadav.
Singh was a former district secretary of the SP and his wife Sunita Singh is a gram pradhaan (village head).
The police reportedly reached the crime scene after several hours which caused an angry mob to raise anti-police and anti-government slogans.