(CNN) -- A Chicago grandmother pleads for a respite as television cameras roll: "Y'all out here killing these innocent people, kids, parents, grandparents, mothers, fathers: It's got to stop. You need to stop."
Semehca Nunn's grandson, Deonta Howard, was in a hospital after being shot in the head Thursday night. In all, 13 people were. None of the victims suffered life-threatening injuries, but that fact offered little relief.
Once again, Chicago is in the spotlight over gun violence; a reminder that it is the city with the highest number of homicides in the country.
An assault-style rifle with a high-capacity magazine was used in the shooting, which appears to be gang-related, Chicago Police Superintendent Garry F. McCarthy said Friday.
The violence "needs to stop," a tearful Nunn said after she came home to find police and television cameras all around. It was only then that she learned that her grandson had been shot in the ear and that the bullet exited through his mouth.
Deonta's condition has stabilized, and he is heavily sedated and will have plastic surgery on his face, Nunn said.
"They said he is going to be OK," she said. "That's what Grandma gave him, strong man, 3 years old, strong survivor."
The other victims include two 15-year-olds who were listed in stable condition, said Officer Ron Gaines of the Chicago Police Department. The rest were adults ages 21 to 41.
Video from CNN affiliate WLS-TV showed police had taped off an outdoor basketball court at Cornell Square Park.
No suspects were in custody as of Friday, and police were focused on interviewing witnesses and victims and gathering any video that may be available.
"We need to keep illegal guns and military-type weapons out of our communities," McCarthy said. "Illegal guns drive violence. Military-type weapons, like the one we believe to have been used in this shooting, belong on a battlefield, not on a street or in a corner or in a park."
The nation needs a ban on assault weapons and high-capacity magazines, he said.
"It's a miracle in this instance there have been no fatalities based on the lethality" of the weapon used Thursday, McCarthy said.
There was a basketball game being played when the shooting happened, the police superintendent said. People were enjoying the park as they do on any other day.
The shooting prompted Mayor Rahm Emanuel to cancel a trip to Washington.
"Senseless and brazen acts of violence have no place in Chicago and betray all that we stand for," the mayor's office said in a statement. "The perpetrators of this crime will be brought to justice and prosecuted to the full extent of the law. I encourage everyone in the community to step forward with any information and everyone in Chicago to continue their individual efforts to build stronger communities where violence has no place."
"It's pretty frustrating, it's very disappointing this is happening in our neighborhood once again," said the Rev. Corey Brooks, a spokesman for the 3-year-old's family.
On any given day, any child in the park or walking to school can be shot, until the community does something about it, he said.
"The truth is that in Chicago, we are facing murders every single day on the south side and west side," Brooks said. "Blacks and Latinos are facing extreme violence."
Illinois Gov. Pat Quinn said he was saddened by what he called "horrific violence."
"We pray for the swift recovery of all the shooting victims, and our hearts go out to their families," he said in a statement. "This senseless violence must be stopped."
The January shooting death of another child, 15-year-old Hadiya Pendleton, brought national attention to Chicago because the band majorette had performed in Washington at events surrounding President Barack Obama's inauguration in January.
The president invited Pendleton's parents to his State of the Union address in February. Obama mentioned her in that speech and a few days later when he returned to Chicago, his hometown, for another speech in which he pressed for stricter gun laws.
Police charged two men in Pendleton's death. They said the two were gang members seeking revenge and mistook Pendleton for someone else.
The FBI's annual crime report this week showed Chicago had 500 homicides in 2012, up from 431 in 2011 and more than any other American city. Chicago officials have said homicides this year are below the 2012 pace.
Still, Chicago does not have the highest homicide rate in the United States. That unwanted distinction belongs to Flint, Michigan, with one homicide for every 1,613 residents, according to the FBI data. Detroit is close behind, with one killing for every 1,832 residents.
In 2012, the number of violent crimes increased by 0.7%, compared with the previous year, according to the FBI figures.
Chicago bans some semiautomatic weapons and high-capacity magazines, and restricts handguns.
CNN's Katherine Wojtecki contributed to this story from Chicago. Kara Devlin, Shawn Nottingham, Tina Burnside and Jennifer Feldman contributed to this report.