"Two people came on a motorcycle, opened fire at the security guard and took away a bag containing around Rs.1.5 crore in cash," Joint Commissioner of Police Sandeep Goel told IANS.
Police also found three mobile camera footages showing two men on a black colour pulsor motorcycle with the pillon rider carrying a pistol and the looted bag. The footages were recorded by eyewitnesses.
The guard was identified as Govind, who received gun shot wounds on his head and chest. He later succumbed to his injuries in hospital, police said.
He was a native of Uttar Pradesh's Etah and was living in Delhi for the past few months.
The incident took place around 11 a.m. when the cash van came to refill a Citibank ATM in north Delhi's Kamla Nagar market area, police said.
Govind was accompanied by another security guard and two bank employees.
The bikers, who were following the van, opened fire at him when he came out of the vehicle. They snatched away the bag the other guard was carrying and brandished their weapons in the air to escape, police said. They were also wearing helmets.
The critically injured guard later succumbed to injuries in AIIMS
The van occupants told police there was more cash in the van which they had needed to refill other ATMs in the city.
Police said they have collected CCTV footage from the spot. They have questioned several people including the bank employees.
Several teams of police are conducting raids in Delhi as well as national capital region in search of the robbers.