CHICAGO (CBS) — While overall crime is down since last year, Chicago saw a big increase in fatal shootings last month, which was the deadliest September in more than a decade.

Compared to the first nine months of last year, murders were up 21 percent through the end of September. Shooting incidents were up 19 percent, and the number of shooting victims was up 14 percent. Overall crime – including robberies, burglaries, and thefts – was down 7 percent.

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The rise in murders so far this year is due in large part to an especially violent September. At the end of August, murders were down 7 percent compared to the first eight months of 2014.

The Chicago Tribune reports last month was the deadliest September since 2002, with at least 60 murders citywide.

Police Supt. Garry McCarthy said the department has initiated a new plan to track illegal weapons, and reduce the number of shootings. The plan includes assigning every illegal gun possession case to a dedicated detective who will track the “origin and flow” of the gun. Police will use that information to prosecute anyone who illegally transferred or sold the gun at any point.

“We are handling every single gun arrest as if it were a robbery or a burglary, with a detective response, and gathering of evidence, to ensure that we can do everything that we can to ensure that that case gets prosecuted to the fullest extent that we can,” McCarthy said in an interview on the CBS 2 Morning News. “That’s something that we’re seeing some results on already. We’ve been doing it for about two-and-a-half months, and the fact is we’re getting through those preliminary hearings. We’re getting better prosecutions, working closely with the state’s attorney.”

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The department also will “embed” violent crime detectives in every district to improve collaboration.

“We know that gang violence is the number one cause of what’s happening on the streets, and we’re gathering more and more intelligence, and trying to refine that intelligence to intersect issues before they happen,” McCarthy said.

The city also will prioritize certain city services, such as street light repairs, in high-crime areas that need them most.

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Police said, through the first nine months of the year, they have recovered more than 5,419 illegal guns, and made 2,242 gun-related arrests.