Abu Sayyaf kidnaps people. They either behead the victims, rarely release the victims, ands asks for $$$ right up front. They don't shoot, shoot, shoot, and eventually ask for money. The exception that I can recall was one American they beheaded and asked for $$$$ anyway. Abu Sayyaf hates Christians, hates Americans, and uses their ill-gotten gains for terrorism.
How do we know this whole shooting spree wasn't preceded by a blackmail demand? It is possible that this could have started with blackmail demand and when he/they didn't get what they wanted, the shooting started.