Members of Detective branch of police have arrested two more suspected last night in connection with the murder case of Mahmuda Khanam Mitu, wife of police superintendent Babul Akter.Debdas Bhattacharya, additional commissioner (Crime and Operation) of Chittagong Metropolitan Police said DB arrested the duo, primarily identified as Shahjahan, 25, and Saidul Sikdar Shakur, 36, were arrested from Rangunia upazila of the district.Shakur is the brother of Kamrul Islam Sikdar Musa, the mastermind behind the killing, police said.The other arrestee was present during the murder, the CMP official added.On June 5, three assailants stabbed and shot Mitu, wife of SP Babul Akter, a cop who spent most of his time curbing militancy, dead when she was taking her son to his school bus stop at GEC intersection in the port city.