CHICAGO (CBS) — Two people were killed and 13 others were injured in a mass shooting in during a party in the Park Manor neighborhood early Sunday.

Police recovered four guns inside.

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The shooting happened at 4:41 a.m. at the South Side Think Tank, 6798 S. South Chicago Ave. The building houses a make-shift tow company and auto repair business, but there was a bar set up, police said.

As CBS 2’s Marissa Parra reported, people who had been dancing in the garage were suddenly running for their lives.

A man and woman did not make it. Rayneesha Dotson, 30, of Morgan Park, and Lionel D. Darling, 39, of West Pullman, were pronounced dead at the scene.

“Unfortunately, these are normal situations here in Chicago,” said activist Ja’Mal Green.

The makeshift rave in the garage was packed – in what people told Parra is a common phenomenon.

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“There’s actually a bar set up inside,” said police Supt. David Brown. “It might have been an old lounge that was converted.”

Videos of the shooting and the aftermath made the rounds online, along with theories and rumors as to who was behind the gunfire and why it started to begin with.

“They talk about it being a petty reason. These are literally situations where folks don’t have conflict resolution skills, so they meet the person they’re mad at and use a weapon,” Green said. “If you know any of these people that were shooting, please speak up – because we need to get them off of the streets.”

Police said the victims ranged in age from 20 to 44.

Several of those who were shot were in and out of surgery late Sunday. As of Sunday night, no one was in custody.

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Police were working Sunday with the Department of Business Affairs and Consumer Protection to determine who owns the building and businesses and if there have been any previous violations.