While authorities continue to dig for more clues as to who kidnapped 4 people on Samal island in Davao del Norte, Davao City Mayor Rodrigo Duterte claims the group behind this is linked to the Abu Sayyaf Group. CNN Philippines takes a closer look at the Abu Sayyaf's history and its atrocities in the past. – This report aired on CNN Philippines’ Network News on September 28, 2015.
