BOSTON, Dec. 12, 2017—The man accused of shooting of 21-year-old Duncan Ketter to death in East Boston was arraigned today on a murder charge and two co-defendants have also been held on high bail, Suffolk County District Attorney Daniel F. Conley said.

THORUS O’BRIEN (D.O.B. 5/16/99) of Brockton was held without bail at prosecutors’ request during a hearing at East Boston Municipal Court today. O’Brien is charged with murder, armed robbery, and unlawfully carrying a loaded firearm.

Yesterday, a 16-YEAR-OLD JUVENILE was arraigned in the Suffolk County Juvenile Court on a charge of delinquency, to wit: armed robbery and armed assault with intent to rob. His bail was set at $100,000. Another man, DEMETRIUS CAST (D.O.B. 6/2/97) of Everett, aces similar charges as an adult. He was held on $350,000 cash bail and his open bail in unrelated Middlesex County cases has been revoked.

Assistant District Attorney Catherine Ham of the DA’s Homicide Unit told Judge John McDonald today that the juvenile contacted a woman known to him and arranged to purchase a quantity of marijuana on Sunday afternoon. Ketter was with this woman at the time of the planned transaction.

The juvenile allegedly brought Ketter and the female into a small sport-utility vehicle to exchange the marijuana for cash. Cast was in the back seat; unbeknownst to Ketter or the woman, however, O’Brien, was also inside, hidden in the rear cargo area of the vehicle. O’Brien allegedly revealed himself as the vehicle was in motion, producing a firearm and demanding marijuana from the woman and Ketter. When he met with verbal resistance, O’Brien allegedly fired, fatally injuring Ketter and striking Cast in the arm. The group allegedly threw Ketter and the woman from the vehicle onto the street, traveled to Revere, and let the juvenile and Cast out as well.

Erin O’Connor is the DA’s assigned victim-witness advocate. O’Brien was represented by attorney John Morris. He will return to court on Jan. 16.

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All defendants are presumed innocent until and unless proven guilty beyond a reasonable doubt.