Rapid Action Battalion (RAB) arrested a man named Ahad Ali, 35, from Pallabi in the capital on Wednesday night over his alleged involvement and planning in killing Brigadier General (Rtd) Wazi Ahmed Chowdhury.RAB claimed that, Ahad is the mastermind behind the killing of Wazi Ahmed. Mufti Mahmud Khan, Director of Legal and Media Wing of RAB headquarters, confirmed the matter to Jagonews24.com. Further details regarding this matter would be disclosed later, he added.