Hundreds of people smashed windows, stole from stores and clashed with police early Monday in Chicago’s Magnificent Mile shopping district and other parts of the city’s downtown.

Chicago police exchanged gunfire with looters and arrested more than 100 people after crowds swarmed the luxury commercial district, police said.

Police Superintendent David Brown called the outbreak “pure criminality,” and Mayor Lori Lightfoot sought to distance the incident from the “righteous uprising” in response to the death of George Floyd at the hands of Minneapolis police on May 25.

“This was not an organized protest. Rather this was an incident of pure criminality,” Mr. Brown told a news conference.

At least 13 officers were injured, and a security guard and a civilian were struck by gunfire, Mr. Brown said.

Social media images showed storefronts bashed in and people fleeing stores with arms full of goods.

Stores miles from downtown were also ransacked, with parking lots littered with glass and items from inside the stores. Clothes hangers and boxes that once contained television sets and other electronics were seen—evidence that thieves had taken racks of clothes and removed them from the hangers.

It was not immediately clear what led to the unrest, which began shortly after midnight, but anti-police graffiti was seen in the area. Hours earlier, dozens of people had faced off with police after officers shot and wounded a person Sunday in the city’s Englewood neighborhood, located about 10 miles away.

As police questioned a 20-year-old suspect, he fled, firing at the pursuing officers, Mr. Brown said. Police returned fire and shot the man, who was hospitalized and expected to survive.

“After the shooting, a crowd gathered…Tempers flared, fueled by misinformation as the afternoon turned into evening,” Mr. Brown said.

A number of social media posts encouraged looting in central Chicago, Mr. Brown said.

In response to the social media posts, police sent 400 officers into the area, where they were met by caravans of people arriving in cars, Mr. Brown said.

As officers arrested one man carrying a cash register, shots were fired at them from a passing vehicle, and police fired back, Mr. Brown said.

Mr. Brown pledged a police crackdown in central Chicago, assigning officers to 12-hour shifts and canceling days off.

This report contains information from Reuters and The Associated Press.