Sambalpur, June 24: A private security guard today gunned down an assistant security sub-inspector of Mahanadi Coalfields Limited (MCL) at its headquarters at Jagruti Vihar in the Burla police limits.

The incident took place at the main gate of the MCL headquarters. The accused, Binod Bihari Tripathy, 45, killed Biswajit Biswas, 44, at 11.15am. "Primary investigation revealed that the accused shot at Biswas over duty assignment," said police.

Tripathy fled the spot with the gun on his motorcycle. Biswas was immediately rushed to Veer Surendra Sai Institute of Medical Sciences and Research, where he was declared dead. Sources said Tripathy had been angry with Biswas, as the latter had not assigned any duty to him for the past six days because of alleged misconduct. This morning, Tripathy had gone to Biswas's house and threatened him of dire consequences if he was not allowed to resume work.

Biswas was a native of Bongaon in Bengal. MCL public relations officer Diken Mehera said a departmental probe would be conducted into the incident. "A police investigation is also being launched," said Mehera. said four security guards were at the main gate when the incident had taken place. "We overpowered Tripathy and rushed Biswas to the hospital," said Pradeep Mishra, an armed security guard, who was at the main gate during the incident.

Burla police station inspector-in-charge Tophan Bag said: "The accused fired one round from his double-barrelled gun. The bullet hit the abdomen of the deceased."

Bag said a case had been lodged with Burla police in this regard and a manhunt was on to nab Tripathy.