The incident took place on Saturday. The bike-borne men with their faces covered first threatened the shopkeeper, they said.
When the shopkeeper objected, one of them shot him in the leg, police said.
The men had covered their faces with a cloth and helmet while entering the shop and efforts are being made to nab them, police said.
The firing led to a ruckus in the area but no one else was injured except the shopkeeper, they said.
The incident caught on CCTV camera showed the three bike-borne men entering the hardware shop on Saturday evening. They were seen allegedly threatening the customers and staff inside the shop. They then started opening the drawers of the shop''s counter, police said.
The footage showed the three men pointing their pistols at the shopkeeper and demanding money from him. When the shopkeeper tried to resist, one of them shot him in his leg, police said.
The injured shopkeeper was admitted to a nearby hospital for treatment, a senior police officer said.
The men then fled with the cash and valuables on their bike, he said.
Deputy Commissioner of Police (Outer North) Rajiv Ranjan Singh said, "An FIR has been registered under stringent provisions of the law and investigation has been taken up. Multiple police teams of outer north district are working round the clock to bring the culprits to book." PTI AMP TDS