The city’s mayor, Firhad Hakim, said on Saturday that chief minister Mamata Banerjee was very annoyed about arms making their way into the state from neighbouring states when he was asked about the attempt to rob a family in Tollygunge on Thursday.

“The chief minister is very annoyed. I was in the room. She asked the police commissioner and the Bengal police where these arms were coming from. She asked whether she would have to go and seize the arms herself. Why isn’t there a police network and how are these arms making their way across the border?” Hakim said.

A man whom the family engaged as a sweeper in their eighth-floor Lake Avenue apartment allegedly smuggled two men into his employer’s house and tried to rob him at gunpoint on Thursday evening.

While fleeing, the men allegedly fired one round in the air to scare away neighbours, police said.

The plan to rob the Lake Avenue apartment of Debasish Dey was drawn up by Sandip Das, the sweeper, whom the Deys had engaged for the last two months, the police said after questioning Sandip, 28, in custody.

“After drawing up the plan, Sandip briefed his accomplices, Bablu Das and Subhas Das. He told them if they were successful their lives would be made because Debasish was a rich man who owned the nine-storeyed building,” said a senior officer.

“Bablu and Subhas work as labourers at a construction site in New Town while Sandip is a New Alipore resident. The three hail from Jharkhand.”

On Thursday, the trio entered the eighth-floor apartment of the building at 68 Lake Avenue and tried to rob Debasish at gunpoint. His wife Poonam’s screams for help alerted neighbours and scared the men. While fleeing, one of them opened fire near the staircase trying to clear off their exit, Debasish said.

The Deys own the building and the rest of the apartments are rented out to tenants.

The three accused were arrested on Friday. They were produced before Alipore court and remanded to police custody till April 15.

“A few days before the attempted robbery, Sandip came with the two accomplices and took a recce of the building, the entrance, the elevator and the compound wall. Some of the residents had complained to Debasish about the movement of unknown persons,” the officer said.

“It appears the three were not hardened criminals.”

On Saturday, police sought the antecedents of the three accused from their counterparts in Jharkhand. Senior officers said it was vital to know how the trio accessed a firearm. The empty cartridge has been sent for forensic examination.

“We have learnt Jharkhand police carried out multiple raids on illegal country-made arm manufacturing units in Dumka, Giridih and Deogarh over the last few years. The gun used to fire a single round was country-made. It remains to be seen whether the three had purchased it from someone,” the officer said.