CHICAGO (CBS) — Police issued a community alert Saturday about robberies involving large groups of young people in Millennium and Grant parks downtown.

The robberies both happened during the evening hours this month. In each instance, the assailants surrounded the victims in the park and took their property by force.

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The first incident happened on Friday, May 21 at 7:20 p.m. in the 200 block of East Randolph Drive in Millennium Park. The second happened at 9:46 p.m. Wednesday, May 26 in the 1100 block of South Michigan Avenue in Grant Park.

The assailants are young men and women between the ages of 14 and 20 in large groups.

Anyone with information on the robberies is asked to call Area Three detectives at (312) 744-8263.

Police have noted repeated issues involving young people gathering downtown and often starting fights with each other. Last weekend, nine people were arrested after getting into fights in and around Millennium Park.

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A man was also shot in the Loop very early last Sunday morning, though it was not specified whether the incident was related to the large crowds and fights in Millennium Park.

Police said at 12:39 a.m., the 20-year-old man was walking in the 100 block of North Wabash Avenue, just west of Millennium Park, with a group of people when a man in another group fired shots and grazed his leg. The victim said he did not know anyone in the group that included the gunman and refused medical treatment on the scene.

Groups of young people flooding downtown Chicago and getting into fight have been a concern for several weeks. One alderman last week said the city needs to stop the crime that comes with this fast, to send a message that these crimes won’t be tolerated heading into summer because it is not the first time this has happened.

The concern is this year, it could get worse.

Three weeks ago, a CBS 2 photojournalist saw someone throwing things at a Chicago Police Department cruise and trash cans and planters knocked over as large groups of teens moved through downtown causing what police called “disturbances.”

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“If we look the other way and allow it to happen, it is only going to get worse as the summer goes on,” said Ald. Brian Hopkins (2nd). “It’s just a matter of time before someone is hurt, if not killed because there have been some weapons involved in this, too.”

CBS 2 Chicago Staff