BOSTON (CBS) – A grand jury indicted a 22-year-old man Friday for starting the events that led to a 26-year-old Boston woman being fatally shot along a Dorchester parade route in August, officials say.

The Suffolk County District Attorney’s office and Boston Police Commissioner William Evans announced Saturday that Wesson Colas has been charged with first-degree murder and armed assault with intent to murder.

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He allegedly pulled a gun and raised it at members of a rival group along a Dorchester parade route on Aug. 23.

Prosecutors say Keith Williams, 18, a member of the second group, fired his gun several times at Colas, missing him and instead fatally hitting Dawnn Jaffier, who stood about a block away, and a 20-year-old surviving victim that stood three blocks away.

“The death of an innocent victim is a predictable outcome when you pull a gun on armed rivals in the middle of a crowded street,” District Attorney Daniel Conley said in a statement.

“Dawnn Jaffier was that innocent victim, and we intend to hold the people responsible for her death accountable in a Suffolk County courtroom.”

Colas was indicted on a murder theory adopted by the Supreme Judicial Court’s 1997 decision in Commonwealth versus Felix Santiago, 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. That theory has been used twice in murder trials in Suffolk County in 2007 and 2008, respectively.

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Earlier this year, Williams was indicted for first-degree murder in Jaffier’s killing, armed assault with intent to murder for injuring the surviving victim during the same volley of shots, and unlawful possession of a firearm.

The grand jury also indicted Jordan Reed, 22, of Randolph, with being an accessory after the fact to Jaffier’s murder.

He is accused of acting with Williams to hide the .357 caliber revolver used in the shootings on Drummond Street shortly after the incident.

Police arrested Colas on Friday and Reed Saturday at the Essex County House of Correction.

“I’m extremely proud of my detectives,” Evans said. “It is their hard work and perseverance on Miss Jaffier’s case that have led to the arrests of these two additional suspects. I’d also like to thank those in the community who stepped forward to assist our officers.

“The information you provide is invaluable to investigations like this one. We hope that these indictments can bring some peace of mind to the Jaffier family.”

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Colas and Reed are slated for arraignment Monday in Suffolk Superior Court.