Dhaka, July 1 -- The family of Zakir Hussain cannot answer the one question that has haunted them since Friday: why was he killed?

The Dhaka South City Corporation sanitation worker was fatally stabbed after joining the Ashura Tazia procession in Old Dhaka's Sutrapur, leaving behind a grieving family that insists he had neither enemies nor a history of conflict.

Relatives describe Zakir as mentally challenged, with the innocence of a child. He never got into trouble with anyone, they said.

"Whoever asked him to do something, he would do it with a smile. Why would anyone want to kill him?"

The father of three lived with his family in Azimpur and was the eldest of five siblings. Neighbours remember him as gentle, cheerful and well-liked...