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

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

Officers of Tollygunge police station said three men, including the sweeper, have been arrested and charged with armed robbery.

The sweeper, Sandip, was working in the apartment of Debasish Dey on Thursday evening when two unknown men tried to barge into the flat and the trio tried to rob the house at gunpoint, the employer alleged. Screams for help from Dey’s wife alerted the neighbours and scared the men who fled.

While fleeing, one of them opened fire near the staircase trying to clear off their exit route, the owner of the flat said.

The incident happened in the eighth-floor apartment of the nine-storeyed building at 68 Lake Avenue in south Calcutta.

The Dey family owns the building and the rest of the apartments are rented out to tenants.

Neighbours said the building’s main guard mostly remained unguarded because the lone security guard would be busy with other work.

“Sandip had been calling me over the past few days asking when he should come. We had hired him for the last two months. On Thursday evening, he was working both inside and outside my flat and the main door was open. Two men suddenly tried to barge into our house and started to gag me with tape. They tried to tie my hands behind my back as I was standing near the main door,” said Debasish, 64, the owner. This happened just in front of the main door of the flat near the elevator and the staircase.

“Sandip brought two men with him to my flat a few days ago saying they were also from his hometown. Yesterday when I called him, I categorically told him that he should come for work alone,” Debasish told Metro on Friday evening.

He said that Sandip on Thursday had phoned his associates who were hiding in the staircase to call them to the eighth-floor Dey residence.

Debasish’s wife Poonam, 49, said on seeing the men attack her husband she rushed inside to fetch something with which she could hit the men.

“Instead of helping me, Sandip followed me inside and advised me to stay away saying the robbers were armed. He then tried to lock me into the house but I started screaming with all my might,” Poonam said.

The two men panicked at the screams and the sound of people coming upstairs. One of the men allegedly opened fire. The family has shown a mark on the wall of the staircase that they said was the grazing mark of a bullet.

The Deys said Sandip pretended to be “aloof” from the robbers and left later. “His activities were very suspicious,” Debasish said.

Poonam dialled 100 to alert the police.

Checking the register of the apartment, cops found the phone number of the sweeper. They tracked his tower location and detained Sandip early on Friday.

Based on Sandip’s statement, the two others — identified as Bablu Das and Subhas Das — were also detained. All three were taken to Tollygunge police station where they reportedly confessed their crime and were formally arrested.

All three are from Jharkhan’s Giridih, the police said.

They were produced before the court on Friday and remanded in police custody till July 15. “A case of armed robbery has been started at Tollygunge police station. The men apparently came to rob the couple. Since Sandip was known to the couple, he was allowed entry,” said a senior officer of Kolkata Police on Friday.

Chief public prosecutor, Alipore court, Sourin Ghosal, said the police had sought the trio’s custody to investigate deeper into the incident and to recover the gun that was used for the alleged firing.