The incident occurred when Sandeep, a suspended Delhi police constable with his associate Deepak, in an inebriated state, tried to enter the premises of a CISF residential colony around 10:45 PM yesterday, police said today.
"Jaiveer Singh, who was posted as a security guard at the gate, stopped them following which the duo started abusing him. The heated argument soon turned ugly and they started beating Singh mercilessly. They then picked up a stone and slammed it on his head," said a police official.
Some CISF personnel residing in the colony nabbed the duo and handed them to the police.
Sandeep of Dariyapur village in Outer Delhi was dismissed from service in May this year for trying to extort money from commuters, the official said.