Ramgarh circle additional superintendent of police Md Raihan Uddin Kazemi said Arefin primarily confessed to his involvement in the killing but did not disclose the reason behind the murder.
Ansheu Marma, the son of the deceased, said Sharif had also set fire to their house a few days ago and then he lodged a complaint with Ramgarh police station and this might angered Sharif.
Meanwhile, Sharif's father Abu Ahmed said his son had been suffering from mental illness for the past few years and was given treatment in different places.
However, local councilor Ahsan Ullah said Sharif is drug-addict and local people has many complaints against him.
A case was filed in this regard, said the ASP.