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PITTSBURGH (CBSMiami) – Large crowds of protesters blocked streets in East Pittsburgh, Pennsylvania calling for change after an officer shot and killed an unarmed 17-year-old.

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Cellphone video appears to show Antwon Rose Jr. running from police on Tuesday night. Three gunshots can then be heard.

“What do we want? Justice! When do we want it? Now,” chanted protesters as they filled the streets on Wednesday, at one point blocking a law enforcement vehicle.

They’re demanding answers in Tuesday night’s deadly shooting.

“It still doesn’t feel real that he’s, he’s gone,” said Rose’ friend Mian Laubscher.

Allegheny County Police Superintendent Coleman McDonough said he understands the community’s reaction.

“I understand in today’s atmosphere, any time a young man is killed, there’s cause for outrage in some areas,” said McDonough.

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The officer involved in the shooting has been placed on administrative leave as it is investigated.

“I would urge people to give us time to conduct an objective investigation, to gather facts,” said McDonough.

McDonough said the vehicle Rose was in matched a car involved in a nearby drive-by shooting. One person in the car was detained and later released.

Police said they found two firearms in the vehicle. Rose was unarmed as he and another suspect ran away.

Rose’s uncle said he sees rage growing in his community amid reports it was the officer’s first day on the job.

“The police officers, I know they got a very hard job and everything but you know what, you gotta be fit for the job,” said James Rose.

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City officials say the officer, who has not been named, was sworn in hours just hours before firing the fatal shots that killed Rose.