The incident occurred during a disturbance at about 7:13 p.m. in the 4700-block of North Racine Avenue in the alderman's 46th Ward, police said.
Alderman Cappleman suffered minor injuries and refused medical attention, police said.
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A suspect was taken into custody, police said.
Further details on what led up to the incident were not immediately available.
Cappleman released a statement Sunday that read:
"Last night I was assaulted by an individual in our community. I am completely fine and my injuries were minor. The police arrive at the scene and took this person into custody.
The incident began as I was responding to a text from an upset resident about a group of intoxicated individuals at the corner of Racine/Leland. This area has a history of this type of issue on and off for the past few years, but it has increasingly picked up in the last couple of months.
I know the individual who assaulted me. I have sat with him numerous times to help him address his addiction issues that have also led to him being without a job and a home. This man's life has been overtaken with his addiction. I continue to push for interventions that get people the real help they need.
The community suffers when this type of behavior takes over a street corner. Many residents who live near the intersection of Leland and Racine do not feel safe walking down the sidewalk in their neighborhood while this activity is happening. We must remain mindful of what these individuals and families are going through as well.
Lastly, I owe it to myself, my husband, my family, and my community to be more careful while I work. I will keep this in mind as well moving forward.
If you or someone you know is suffering from disordered substance use, please go to Chicago Connects at chicagoconnects.org or contact my office for more resources to get help."