Birbal, resident of Shivpuri colony, received a letter yesterday warning that either he pays the ransom money or face dire consequences, they said.
The victim informed police about the threat who then checked the CCTV footage of Birbal's shop, they said.
Three masked persons can be seen roaming around the shop but their identity is still unknown, they said.
Police have filed a complaint against the unknown culprits and further investigations are on, SHO Varun Kumar said.