BOSTON (CBS) — Boston Police announced on Sunday that they have made an arrest in connection with a shooting on Copeland Street that left four people injured.

According to Boston Police Commissioner William Evans, officers were in the area and heard gunshots ring out just after midnight on Saturday. When they reached the scene, they saw a man holding a loaded 9mm Glock 19 gun and running away. That man was arrested and within the 24 hours that followed, the ballistics unit was able to connect his gun to the shooting.

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Thirty-year-old Anthony Sheffield, of Boston, was charged as a career criminal with three counts of armed assault with intent to murder and unlawful possession of a firearm. He will be arraigned in Roxbury District Court on Monday.

“It was a lot of good police work, believe it or not,” said Evans.

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The Commissioner also they are still looking for more information to try and understand what happened — and to determine if there was a shootout. “It’s active. There was a lot fo shell casing, so we believe there’s more to this particular case,” he said.

Initially, police said no witnesses were talking, something that makes police work even more difficult.

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“With the warm months ahead, I think if we all tell police what happened, maybe people would be afraid to pick up that gun,” Evans said.