Manoj, the son of SP leader Mahendra Pal, was returning home from his factory situated in Anand industrial area in his car along with some of his friends last night when the incident happened, SHO Sahibabad Upendra Yadav said.
Manoj and his friends objected to three persons who were blocking traffic and a heated argument broke out.
In the meantime, a factory guard rushed to the spot and in his bid to pacify them his gun went off, police said.