A group of young men who had been hustled out of a bar for dancing on the tables returned after a while to fire between eight and 10 rounds in the direction of the building, killing a 24-year-old construction materials supplier and injuring two other bystanders.

The incident occurred late on Wednesday outside the curiously named Hard Rocks Bar at the Kabardanga crossing in Thakurpukur, home to scores of supply syndicates battling for a share of the real estate pie on the city's southern fringe.

Rahul Majumdar, a regular at the bar, was a member of one such syndicate but apparently had nothing to do with the incident that triggered the reprisal and led to his death within a few feet of a police kiosk and a Trinamul Congress office.

Sources said the bustling Hard Rocks Bar, owned by two brothers, was shut by the time the 24-year-old arrived on Wednesday night. He had barely started walking towards a cigarette shop opposite the road when the gang reappeared all guns blazing.

Sanjay Chhetri, 32, and Uttam Saha, 40, had a narrow escape, a bullet each grazing their wrists. The duo, who are auto-rickshaw drivers, suffered fractures and were discharged from hospital after treatment.

Witnesses said it was business as usual at Hard Rocks, located on the second floor of a four-storey building called Pabitra Mega Mall, until a group of eight began climbing the tables and dancing to the songs sung by the bar crooners around 10pm. The youths allegedly refused to stop despite repeated requests, prompting two bouncers to intervene.

"The youths began to abuse us and refused to leave. When the bouncers intervened, they threatened us with dire consequences. While leaving, the group said they would come back in an hour to show us their might," bar manager Avijit Rozario recounted on Thursday. "One of them said his name was Nanti and that he was from Renia, near Sonarpur. He said we would have to pay the price for insulting him."

Sources said Nanti Ghosh, a Trinamul worker who runs a syndicate in Sonarpur, and his men had together ordered 18 pegs of whiskey, for which they paid Rs 2,700. When they were forced out around 10pm, some local Trinamul workers stepped out from the adjacent party office and egged on the bouncers, the sources said.

Fearing trouble, manager Rozario went to Haridevpur police station, around 4km away, and lodged a general diary. A police team accompanied him back to the bar.

According to an employee of Hard Rocks, the evicted group returned on motorbikes and an auto-rickshaw around 11pm. The police team was inside the bar then and the youths fled on seeing them, he said.

"The cops asked us to wrap up ahead of time and left. We shut shop 20 minutes before normal and some of our employees had started leaving when two suddenly came running back, saying some youths were firing at them. We immediately downed shutters and hid inside," Rozario said.

Witnesses said the youths, divided into three groups, hurled bombs even as some of them kept firing. Around 30 shots were fired and at least 10 bombs exploded, they added.

Two policemen on duty allegedly locked themselves inside their kiosk while two more deployed at the checkpoint at the crossing, barely 50 metres away, fled, sources said.

"Eight to 10 rounds were fired. We recovered four empty cartridges and two bullet heads. One Bijoy Bhowmik, who was part of the group, was caught while fleeing," said a senior officer in Lalbazar.

Auto-rickshaw driver Sanjay said he was walking back home with a friend when the incident occurred.

"I heard gunshots and before I could make sense of what was happening, a bomb exploded a few metres away and I saw a man slumping to the ground. I was trying to take cover in an alley when a bullet grazed my hand," he recalled.

Nirmalendu Ghosh, who runs a cigarette shop opposite the bar, said some of the assailants had tried to climb the police kiosk to take aim at bar employees fleeing the scene.

The police raided several places in Sonarpur, Bansdroni, Nepalgunje and Thakurpukur but the lone arrest in the case until Thursday night was of Bijoy, who witnesses said had fallen into a drain while trying to flee.

Like the two sides involved in the clash, victim Rahul had a Trinamul connection too. Residents of the area said he was often seen with Ghanasreee Bagh, councillor of Ward 125 of the Calcutta Municipal Corporation.

The neighbourhood where the shooting occurred was part of a panchayat until August 2012, when it was brought under the CMC. The civic election in April was the first for the area as a CMC ward.