The valet, who has not been identified, was seriously injured in the Feb. 7 incident when a bullet struck him in the eye, Suffolk County District Attorney Rachel Rollins said.
Rollins said at a news conference on Tuesday that she believes the worker's retina may have been damaged and his eye is still functioning.
"I personally met with the valet that was struck by a bullet to wish him our condolences for the injury and a speedy recovery," she said, adding that members of her team met with him again to let him know that his injury was the result of an officer firing his weapon.
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Boston police were called to the hospital around 9:20 a.m. for a report of a person with a gun. An investigation later determined that the suspect, Justin Root, had a replica firearm that did not work, Rollins said.
The district attorney said the hospital called 911 following an incident with Root and a security guard during which Root displayed a gun in the waistband of his pants and threatened the guard.
Several officers responded to what Rollins called a "tense and escalating potential active shooter situation." When police arrived, Root had left and was chasing two other security guards down a street. Police arrived at that scene and Root stopped his chase and directed officers up the street "in an apparent attempt to deflect police's attention elsewhere."
"During the ensuing confusion, Mr. Root encountered a Boston police officer who observed a gun in Mr. Root's waistband," Rollins said.
The officer ordered Root to stop, but the suspect removed the gun, pointed it at the officer and began to pull the trigger. The officer fired several shots. A second officer witnessed the encounter and also discharged his weapon.
Rollins said the investigation will determine if both officers acted appropriately when they discharged their weapons and injured a civilian.
Root was also injured in the gunfire but was able to jump in his car and flee. He drove into Brookline where he crashed into several parked cars before stopping, getting out and once again displaying a gun.
Officers opened fire, fatally injuring Root. He was pronounced dead at a hospital.
The incident involved multiple law enforcement agencies, including Boston police and Massachusetts State Police.
Minyvonne Burke is a breaking news reporter for NBC News.