Chaos erupted on Chicago's South Side on Tuesday evening as three masked men allegedly attacked a security guard at a Family Dollar store, leading to critical injuries for one assailant after an intervention by an unidentified shooter. CBS News Chicago reports that the incident, which is being investigated as an attempted robbery, took place around 7:19 p.m. at the location of 2346 E. 79th St., near Yates Boulevard.

After striking the unarmed guard with a firearm, the three suspects fled the store when, according to ABC 7 Chicago, "someone outside of the store took out a gun and shot one of them, a 60-year-old man, in the chest." The 60-year-old man received immediate medical attention at the University of Chicago Medical Center, where he remains in critical condition under police custody with charges pending.

The incident has prompted a full investigation by Calumet Area detectives, as per CBS News Chicago. No further information has been provided about the whereabouts of the other two individuals or the identity of the person who fired the shots, as the police are still piecing together the evening's jarring events.