The contractor named Sanjiv Jaiswal bought three corn on the cobs late Monday night from Pramod, who put up his cart near his house regularly,but refused to pay.
As the corn cob seller protested insisting on payment, Jaiswal flew into a rage and fired at him, SP (city) Ajay Singh said.
As the petty trader fell on the ground bleeding, the contractor,probably realising the gravity of what he had done, shot himself and died on the spot, the official said.
Jaiswal's friend Naresh, who was with him at the time of the incident, is being interrogated, the SP (city) said.