He was believed to have been the protégé of Azahari Husin and under Azahari's guidance Dulmatin became an electronics specialist and bomb making expert. He participated in the car bomb attack on the Philippine ambassador in Jakarta on 1 August 2000 and assembled the timers for the 38 Christmas 2000 church bombings in Indonesia which killed 19 people.[2][3] He was one of the masterminds behind the 2002 Bali bombings in Indonesia which killed 202 people, including 27 from the United Kingdom and 88 Australian citizens. Working alongside Azahari, Dulmatin helped to assemble the car bomb and explosive vests used in the attack.