Unidentified assailants on Monday night gunned down Rajibul Islam at his brother's wedding reception and wounded four others in Motijheel.

The locals said Rajib became a rival of to the brother of a BNP minister as he had changed his godfather. The change even caused cancellation of a business contract he had earlier obtained, they added.

Investigators have also "figured out" three more points -- extortion, rivalry over tenders and establishing supremacy in the area.

The locals also pointed at an internal conflict in the local unit of Jubo Dal, the youth wing of ruling BNP.

Witnesses said Rajib cowered at the Railway Officers Club seeing the assailants approaching towards him. It suggests he might have known the killers and their intention, they added.

Police are scrutinising the footage of the occasion videotaped that night to identity the killers.

Rajib's uncle Abdul Gafur yesterday filed a case against unknown men with Motijheel Police Station.

Police said Rajib was known as a criminal in the locality and was accused in at least 10 cases filed with Motijheel Police Station. He was also a charge-sheeted accused in seven cases, they added.