In 1994, four members of the White Father mission in Tizi Ouzou, Algeria, were murdered in their home. In 1995, MacWilliam volunteered to go to Algeria to re-open the mission in Tizi Ouzou. He served in Algeria between 1995 and 2008, during which violence against Christians increased and the Civil War was fought. He then worked in Tunisia. He has served as Superior Provincial for North Africa (covering Algeria and Tunisia) since 2015.