Wilhelmus JJ Lutz Geertman was stunned. He raised his hands when he saw the two men with handguns.
They forced him to kneel and shot him in the back before snatching the bag of money he was holding.
The killers fled on a Honda motorcycle driven by a man in a raincoat. They were tailed by a red Mitsubishi car.
Colleagues of Geertman on Thursday cited witnesses' accounts and video footage in pointing at telltale signs that the Dutch aid worker was "executed" for his political advocacy and in raising doubts to police claim of a case of robbery with homicide.
Geertman, 67, executive director of the nongovernmental group Alay Bayan-Luson Inc. (ABI), was killed on Tuesday in front of his office inside L&S Subdivision in Barangay (village) Sto. Domingo, Angeles City.