The victim was shot in the hand and was in serious condition.
The shooting happened as people gathered for a memorial at nearby 70th Street and Throop to honor Albert Vaugh Jr., the 23rd CPS student to die a violent death this school year.
Eighteen-year-old Vaughn was beaten to death Saturday night with a baseball bat.
Vaughn's grief-stricken sister mourned the loss of her older brother as he became yet another student to fall prey to violence.
"He's my brother. I love him. I'm going to miss him. It's going to be hard without him," Amanda Vaughn, the victim's sister, said.
"It just think it's a dream, but it's not," said the victim's father, Albert Vaughn Sr.
Witnesses say Vaughn was beaten to death Saturday night as he tried to help a neighbor break up a party she was throwing for her eighth grade son in the 7000 block of South Throop Street.
"It's terrible because it was my son's birthday party., and Albert was really just trying to make all the kids go home. The party was supposed to be over at 10:30. Curfew was at 11:00. We were trying to get everybody in before curfew," said Trulanda James-Fields, the victim's neighbor.
Fields also said other neighbors who live on the block tried to help disburse the kids, as well. They even called police, but for some reason, Vaughn got into an altercation with an unidentified man.
"By it being two different blocks, they felt like one couldn't tell the other what to do, and that's how it escalate," party host Jimmy Madden said.
That's when friends say a 22-year old man struck Vaughn twice in the back of the head with a baseball bat, killing him. Vaughan died of his injuries at Advocate Christ Medical Center in Oak Lawn.
Sunday morning at a memorial for Vaughn, some area residents remained angry, saying police officers already on the scene could have done more to save the 18-year-old's life.
"They're supposed to serve and protect. Where do they serve and protect? We called them out to do their job and they didn't do their job last night," witness Sunday Turman told ABC7 Chicago.
Albert Vaughn Jr. was set to graduate from Percy Julian High School in June, the same school as slain student Blair Holt, who was shot to death on a CTA bus in May 2007.
Vaughn's older brother said he hopes others will learn from this tragedy.
"Walking away is the best thing to do. Be the bigger person and walk away," Cortez Vaughn said.
Police have recovered the weapon used to beat Vaughn. Authorities arrested one person, but no charges had been filed as of Sunday night.
At Julian High School last Friday, fundraiser was held to raise money to build a permanent memorial to Blair Holt. Meanwhile, crisis counselors are expected to return to the school Monday to help students and staff deal with the latest tragedy.