Extramarital affair between Arzina and her subtenant Shahin Malik led to the murder of her husband Jamil Sheikh and daughter in the capital's North Badda, say investigators.

Shahin, who along with his wife and child lived in a small room as a subtenant of the victims, hit hard in the head of Jamil with something hard when he was in sleep.

Wishing not to be named, two police officials investigating the double murder said Shahin strangled the victim's daughter Nusrat Akter Zidney, 9, as she saw Shahin killing her father. 

According to the officials, Shahin entered the room after Arzina opened the door of her room.

Soon after the killings, Shahin, a construction worker, along with his wife Masuma Begum and their only child fled in the early hours of Thursday, the officials told The Daily Star yesterday.

Contacted, Mostaq Ahmed, deputy commissioner (Gulshan division) of Dhaka Metropolitan Police, said, “We've made a remarkable progress in the probe.”

But he did not go into detail.

Police arrested the couple in Khulna early yesterday.

A Badda police team arrested prime suspect Shahin and his wife with the help of Batiaghata police in Khulna, Ashraful Kabir, senior assistant commissioner (Badda zone) of DMP, told this correspondent. 

On Thursday, Jamil's brother Shamim Sheikh filed a case against Shahin and Arzina in connection with the double murder.

The murder of Jamil, 38, a private car driver by profession, and his daughter Nusrat, a class-III student, took place on Thursday, barely 12 hours into the killings of a mother and her son at their house in Kakrail.

When Arzina's husband and their daughter were found murdered, Arzina told locals that four unknown people stormed their house and killed the two, said Jamil's another brother Imrul Islam Ibrahim.