Khia Shanks, an eighth-grader who graduated Thursday, was making water balloons for the big water-balloon fight — a normal occurrence at end-of-year school picnics across the country.

But this end-of-year event at Warren Elementary on the Far South Side ended up being anything but normal.

Instead of balloons flying, there were bullets.

“The kids were running around the playground playing with water balloons,” 14-year-old Khia said. “I went outside and saw a black van drive by and someone fired about five shots.

“I ran inside. I was in shock.”

Two of her schoolmates, ages 7 and 13, ended up being shot, Chicago Police said.

Chicago Fire Department spokesman Larry Merritt said the younger girl was shot in the right thigh while the older girl was shot in the right hand. They were both taken to Comer Children’s Hospital, and their injuries were not thought to be life-threatening.

Still, the fact that a school picnic was interrupted by gun violence encapsulated the violence challenge that police and the public are facing citywide.

“This makes me sick that kids are having an end-of-the-year picnic and they have to get shot at,” Chicago Police Supt. Eddie Johnson said at a press conference outside the school.

Police responded about 1:51 p.m. to a call of “shots fired” at Warren, in the 9200 block of South Jeffery in the Calumet Heights neighborhood.

Police investigate after two students, girls aged 7 and 13, were shot Friday afternoon outside Warren Elementary school on the Far South Side. | Francesca Gattuso/Sun-Times

Several former Warren students who weren’t supposed to be at the picnic tried to get in but were rebuffed by security officers who recognized them, Johnson said.

Those former students, whose ages he wouldn’t give, went and stood on a nearby corner at 92nd and Chappel. “A black vehicle pulled up and began firing,” Johnson said. The youths then “ran back into the picnic, drawing fire into the picnic.

“They were the intended targets, not the kids.”

Police pulled over the black Jeep — now known to have been reported stolen — and three “persons of interest” are in custody, the superintendent said.

Stephaney Branch, Khia’s mother, said she felt “disbelief, but not surprise” and was “seriously looking into home-schooling” her daughter.

Police officers on the Warren School playground, where two girls were hit by gunfire. Their injuries are not believed to be life-threatening. | Leslie Adkins/For the Sun-Times

“I want my daughter to be around other children, but this makes me sad and angry,” Branch said.

The school has about 300 students in pre-K through 8th grade, but does not have a Safe Passage Program, according to the Chicago Public Schools website.

CPS CEO Forrest Claypool said officials will “review every detail” leading up to the shooting and talk to the students involved.

But Claypool added that, “Despite this incident, the schools are still the safest place that children can be. There has not been a shooting incident involving a student at a Chicago Public School in decades. This was a highly unusual situation.”

Two girls, ages 7 and 13, were shot Friday afternoon outside Warren Elementary school on the Far South Side during a picnic that was supposed to celebrate the end of the school year. | Francesca Gattuso/Sun-Times

As a few officers continued to investigate and a helicopter circled overhead, the playground was empty except for a school bag, one white t-shirt and a deflated basketball.

A 56-year-old Warren graduate whose 9-year-old granddaughter now attends the school said the girl was on the playground during the shooting. “She said when she heard shots, she ducked first and then ran,” said the woman, who asked not to be identified.

Jasmine Phillips, the mother of a Warren first-grader, was rushing into the school to find her son after her mother, the boy’s grandmother, told her what had happened.

She said the school didn’t notify parents of the incident. But Claypool said each parent was contacted to pick their child up. And if parents couldn’t be reached, police escorted the children home.

CPS provided a copy of the message, sent by text and automated telephone call: “We want to make you aware that there was a shooting outside of the school today. Two students were injured and immediately transported to the hospital. Their parents have been notified and no other students or staff were hurt in this incident. The Chicago Police Department and CPS Safety & Security are on site, and student dismissal has begun for parents to pick up their children. All parents must come to the school to pick up your child.”

A Chicago police officer investigates a shooting at Joseph Warren School. Two girls from the school were shot Friday. | Leslie Adkins/For the Sun-Times.

All in all, it was another difficult day in a city that has seen more than 1,230 non-fatal shootings and 288 murders so far this year — roughly the same as last year, in which Chicago saw its homicide total eclipse New York’s and Los Angeles’ combined.

“This should make everyone angry,” Johnson said.

Mayor Rahm Emanuel, was meeting the victims’ families at Comer Children’s Hospital, Claypool said.

“I’ve known the mayor for 30 years and I have never seen him so angry,” Claypool said.

Contributing: Lauren FitzPatrick