CHICAGO (CBS) — At least 40 people were shot in weekend gun violence in Chicago, and four of them had been killed.

The incidents included a mass shooting that left two people dead and 13 others wounded at a gathering in the Park Manor neighborhood early Sunday morning. A Chicago Police officer was also shot and wounded Sunday afternoon outside the Gresham (6th) District station.

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The mass shooting took place at a party in the 6700 block of South South Chicago Avenue at South Side Think Tank around 4:40 a.m. Sunday The building houses a makeshift tow company and auto repair business, but there was a bar set up, police said.

The Chicago Fire Department said two people were dead when they arrived on scene, and they transported seven other victims to local hospitals. Fire officials say others may have also driven themselves to hospitals, adding to the number of victims.

A man and a woman were killed. The Cook County Medical Examiner’s office identified the victims who were killed as Rayneesha Dotson, 30, of Morgan Park, and Lionel D. Darling, 39, of West Pullman.

Police said there were 15 people shot in all. The victims ranged in age from 20 to 44.

On Sunday afternoon, a Chicago Police sergeant was shot and wounded Sunday afternoon outside the Gresham District police station. Police News Affairs Deputy Director Tom Ahern said the sergeant and another officer were standing in the parking lot across from the Gresham (6th) District police station, 7808 S. Halsted St., when one of them was struck by gunfire.

Police Supt. David Brown said on Twitter that the sergeant suffered a graze wound to the chin area and was taken to a local hospital in good condition. Ahern said the officer was taken to Advocate Christ Medical Center in Oak Lawn.

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In the first homicide of the weekend, a woman was killed and a man was injured in a shooting in the West Humboldt Park neighborhood. At 9:34 p.m. Saturday, the victims were sitting on a porch when two men came up and shot them both.

A 47-year-old woman was taken to Mount Sinai Hospital with a gunshot wound to the torso and was pronounced dead there. A 51-year-old man was taken to the same hospital in fair condition with gunshot wounds to the right leg. The woman who was killed was identified as Susana Rodriguez.

At 1:06 a.m. Sunday, a man was shot and killed during a domestic quarrel in the 7900 block of South Kimbark Avenue in Avalon Park. Police said the 54-year-old man – identified by the Cook County Medical Examiner’s office as Gino Collins – was in a fight with a 53-year-old woman in a second-floor apartment when he was shot dead. The woman was taken into custody and a gun was recovered, police said.

Meanwhile on Sunday afternoon, a 13-year-old boy was among three people shot in South Shore. At 2:42 p.m., the boy and a 20-year-old man heard shots and felt pain in the 2600 block of East 77th Street.

The boy was shot in the knee and was taken to the University of Chicago’s Comer Children’s Hospital in good condition. The man was shot in the arm and was taken to the U of C Medical Center in an unknown condition.

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A 36-year-old man was also shot. He was wounded in the left thigh and was taken to Advocate Trinity Hospital in serious condition, police said.

CBS 2 Chicago Staff