A 24-year-old man died after a drive-by attack Sunday in the Loop.

Mario A. Guerrero was driving in the 500 block of East Lower Wacker Drive about 3:03 a.m. when someone in a dark-colored SUV fired shots, Chicago police and the Cook County medical examiner’s office said. The suspect drove off west on Lower Wacker.

Guerrero, who lived in Gage Park on the Southwest Side, was taken to Northwestern Memorial Hospital, where he was pronounced dead at 3:34 a.m., authorities said. An autopsy Monday found he died of a gunshot wound to the chest and his death was ruled a homicide.

An off-duty sergeant who was at the scene is being questioned by internal affairs for potentially interfering with the investigation.

Area Central detectives are investigating the shooting.

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