A six-year-old boy was sexually abused inside the bathroom stall of a Chicago McDonald’s over the weekend, police said Monday. 

The victim was in the stall of a River North McDonald’s bathroom shortly after 5:45 p.m. on Saturday when "an unknown offender entered the stall and sexually abused him," the Chicago Police Department said in an email Monday. 

A security guard at the North Clark Street restaurant tried to intervene and stop the suspect, who then grew violent, police said. He allegedly tried to resist arrest when cops arrived at the scene, but was ultimately taken into police custody. 

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Charges against the man – whose name and age were not immediately revealed – were pending. Meanwhile, the young victim was taken to a local hospital. 

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The security guard did not need medical attention. 

Police are investigating the attack.