Patna, June 4 (IANS) Bihar's former deputy inspector general of police Arun Kumar Singh was shot dead by unidentified attackers in Patna Sunday afternoon, police said.

Singh was going from his Kankarbag Colony residence to Rajendra Nagar Terminal railway station when he was attacked, a senior police officer told IANS.

"We have arrested four people, and further investigations are on," he said.

The official said that preliminary investigation showed that the attackers only wanted to rob Singh. However, as the officer retaliated he was murdered.