Odisha health minister Naba Kishore Das, 61, died on Sunday after being shot in the chest allegedly by an assistant sub-inspector of police, who was apparently under psychiatric treatment.

Police officers said Das had stepped off his car around 12.20pm to attend a programme at Brajrajnagar, part of his constituency of Jharsuguda in western Odisha. He was being garlanded by his supporters when ASI Gopal Das allegedly fired two shots from his service revolver. The minister dropped to the ground, bleeding from the chest.

The ASI has been arrested but the motive for the murder remains unclear. Chief minister Naveen Patnaik has ordered a crime branch probe.

“The police officer suddenly came up to the car and shot him (minister). We could not believe what we were seeing. It happened in the blink of an eye,” an eyewitness said.

Das, a Biju Janata Dal MLA, was lifted into his car and driven to the local hospital. He was later flown to Bhubaneswar and admitted to Apollo Hospital, a green corridor having been created from airport to hospital. He died in the evening.

A bulletin from Apollo Hospital said: “The minister was admitted to Apollo with gunshot wounds to the left chest.... On operating (it) was found that a single bullet had entered and exited the body, injuring the heart and left lung and causing massive internal bleeding and injury.

“The injuries were repaired and steps were taken to improve the pumping of the heart. He was given urgent ICU care. But despite best efforts, he could not be revived.”

Jayanti Das, wife of the ASI, a man in his 40s posted at Gandhi Chhak police outpost in Brajrajnagar, said: “I cannot believe it. He has been in Jharsuguda for the last 11 to 12 years. He was under treatment for psychological issues.”

After the firing, the ASI tried to run away but some of those present chased and overpowered him, eyewitnesses said.

Brajrajnagar sub divisional police officer Gupteshwar Bhoi told reporters: “We are examining what the motive could have been.”

Minister Das, a businessman, had represented the Jharsuguda Assembly constituency since 2009, winning on a Congress ticket in 2009 and 2014 and on a BJD ticket in 2019.

He was one of the richest ministers in Naveen’s cabinet with property worth more than Rs 34 crore. He owned a fleet of cars and three firearms: a revolver, a rifle and a double-barrelled gun.

The minister had been in the news last week when he donated a Rs 1-crore urn, made of 700gm gold and 5kg silver, to the Shani Temple Trust at Shingnapur in Maharashtra’s Ahmednagar district.

He was to attend the opening of a municipal office meant to receive public grievances in Brajrajnagar, and a crowd of about 100 people had gathered to welcome him.

Naveen, who visited the hospital, said in a statement: “I am shocked and distressed over the very unfortunate demise of minister Naba Das.”