A former employee of a Cafe Coffee Day outlet in Salt Lake’s AD Block and two of his friends were arrested on Saturday in connection with a robbery at the shop on October 29.

Sankar Das, 20, a resident of Gaighata in North 24-Parganas, had planned the robbery after quitting the job about four months ago, police said.

Das was well aware of with outlet’s working hours, Amit Javalgi, deputy commissioner, headquarters, Bidhannagar commissionerate said.

He had planned the robbery in the morning since he knew there would be only one waiter at the time, Javalgi said.

“Das has told us that the outlet hadn’t cleared some of his dues and so he thought of robbing the shop.”

Das took the help of two of his childhood friends who live near his house, an investigating officer said.

Around 10.20am on October 29, Das sent Biltu Sarkar, 19, and Surajit Roy, 20, to overpower Suvankar Ghosh, the waiter on duty at the time, the officer said.

Sarkar and Roy entered the outlet and one of them held a gun to Ghosh’s head.

Das entered the shop after his friends had tied up Ghosh with his apron and blindfolded him with a shirt. He crawled into the cafe to avoid being captured by the outlet’s CCTV cameras, the officer claimed. Das took Rs 15,000 from the cash register and crawled out of the cafe.

“He stood up only when he was out of the cafe. Once outside, the three walked towards Kestopur canal.

“They took a local train to Gaighata from Ultadanga,” the officer said.

Officers had managed to get hold of the footage from a CCTV camera installed on one of the neighbouring houses.

The camera had captured their faces clearly despite a power cut in the area around the time of the robbery, the officer said.

Ghosh and other employees of the outlet saw the footage and told cops that one of the three resembled Das.

The cafe’s CCTV camera had no footage from 10.10am to 11.30am.

Cops got the mobile phone number of Das from the cafe and put it under electronic surveillance.

The tower location of the phone showed Das was in AD Block on the day of the robbery. “This raised our suspicion as he had quit the job.... We sent a police team to his house and he broke down during questioning,” Javalgi said.

He led them to the houses of Sarkar and Roy, the police said.

The cops are still to seize the gun used in the robbery and the money stolen but they have seized the phones of the three.

Cops are scanning their call details to find out if they had contacted anyone else after the robbery.