On December 10, 2017, 19-year-old Duncan Ketter was killed in East Boston during what prosecutors describe as a planned robbery tied to a drug transaction. Ketter and a female friend were in a vehicle to sell marijuana when a 16-year-old acquaintance set up the sale. An 18-year-old, Thorus O’Brien, reportedly hidden in the back of the car, emerged with a firearm; when met with resistance he allegedly shot Ketter. Both Ketter and his friend were pushed out of the moving vehicle at the corner of Orleans and Marginal Streets.

The investigation produced several arrests. Thorus O’Brien of Brockton was arrested the day after the shooting and charged with murder, armed robbery, and unlawfully carrying a loaded firearm. A 16-year-old was charged with delinquency, to wit, armed robbery and armed assault with intent to rob. Demetrius Cast, 20, of Everett, and Elijah Charles, 18, of Brockton were later arrested and arraigned on armed robbery and related charges.

What information about Duncan or the people involved might help clarify how this ambush was arranged?