According to the police, Deepak Kumar, the security guard of a Central Bank ATM booth in Maurya Lok here, was killed and cash was looted.
Maurya Lok, a posh shopping centre, is known as a safe zone for visitors as patrolling police have been deployed round the clock.
Agitated residents and relatives of the guard blocked the roads and burnt tyres to protest against the incident.
They demanded the arrest of those behind the crime, and a compensation to the family of the victim.
According to the police, prima facie it appears that the armed men killed the guard when he resisted their attempt to loot the cash in the ATM machine.
Patna Senior Superintendent of Police, Manu Maharaj, told the media that the police have began a probe into the incident. "The police will arrest those involved in the crime."
"We have collected CCTV footage and other evidences from the site," Maharaj said.