An argument that began inside Rudy’s Bar in Upper Darby as it was closing early Thursday turned violent, with three people shot, one fatally, police said.

Investigators were searching for the suspect Thursday, according to Police Superintendent Timothy Bernhardt. He said his officers were reviewing hours of video footage from the bar, and planned to release more information on the suspect as soon as he is identified.

The incident began just before 2 a.m., when a group of patrons were getting ready to leave Rudy’s, on Marshall Road, Bernhardt said. A dispute among the group spilled outside, where at least two people drew guns and started firing, he said.

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One man — whom police did not identify — was pronounced dead at the scene. Two other victims, a man and a woman, were taken to Lankenau Medical Center, where they were treated and later released.

The two guns used in the shooting were recovered by police, Bernhardt said. Anyone with information about the incident is asked to contact Upper Darby police at 610-734-3439.