The incident occurred last night when Shiv Singh Saini, grand uncle of the bride, a resident of Bhadholi village, was blessing the newly-wed couple on stage at the function.
Ambah tehsil Sub-Divisional Officer of Police (SDOP) Kishore Singh said some revellers gathered in front of the stage opened fire in air after 'jaimala' ceremony.
"A bullet hit the shoulder of Shiv Singh Saini who was on stage, killing him on the spot," he said.
Though he was rushed to hospital immediately, doctors there declared him brought dead.
Further investigation is on.