By Mary Whitfill, editor-in-chief 

On Aug. 23, 2014, 26-year-old Dawnn Jaffier was shot in the head along a Dorchester parade route at roughly 8 a.m. On Friday, 22-year-old Weeson Colas was charged with first-degree murder and armed assault with intent to murder in her death.

According to prosecutors, Jaffier was a bystander when two rival groups began shooting at each other from across the street that morning. 18-year-old Keith Williams, who fired the shot at Colas’ group that killed Jaffier, was indicted earlier this year on charges of first-degree murder, armed assault and unlawful possession of a firearm.

Colas was indicted on a murder theory adopted by the Supreme Judicial Court in 1997, which stated that “Where the defendant chooses to engage in a gun battle with another with the intent to kill or do grievous bodily harm and a third party is killed, the defendant may be held liable for the homicide even if it was the defendant’s opponent who fired the fatal shot.”

Jordan Reed, 22, was also indicted with being an accessory after the fact when he allegedly helped Williams hide the gun used in the shooting.

Reed and Colas will be arraigned in Suffolk Superior Court.

Jaffier was a graduate of University of Massachusetts Amherst and serving with City Year, an Americorps program, in Boston at the time of her death. She worked at the Hennigan Elementary School.