BOSTON (CBS/AP) — Two men charged with first-degree murder in connection with the shooting death of an innocent bystander at a Boston street festival in 2014 are headed to trial.

Opening statements in the trial of Keith Williams and Wesson Colas were heard Monday in Suffolk Superior Court.

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Prosecutors say Williams and Colas were rivals who confronted each other with guns near a Caribbean festival in Dorchester in August 2014. Prosecutors say Williams fired, but Colas did not.

Dawnn Jaffier. (Photo from Facebook)

A bullet struck and killed 24-year-old Dawnn Jaffier, a city youth worker, who was marching in a parade for the festival a block away.

Jaffier was a Boston Public Schools graduate who returned to the district to work as an after-school tutor and a coach at Playworks, a community organization, according to Boston Public Schools. Jaffier also worked as a lunch monitor at the Hennigan School. She also served with City Year at the Maurice J. Tobin school.

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Under state law, both men face murder charges and will be tried together even though they are rivals.

“These two men, decided on their own, to take an entire section of Blue Hill Avenue between Charlotte Street and McLellan Street as their very own,” said Assistant District Attorney Mark Lee.

Williams’ attorney claims the gun was never linked to his client. Colas was on his way to work, and was not carrying a gun, his attorney said.

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.

Their defense lawyers had asked a judge to separate the cases.

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