Updated story

After 13 people, including a 3-year-old, were shot Thursday night in a park on Chicago's Southwest Side, Mayor Rahm Emanuel canceled a Friday appearance in New Jersey and meetings in Washington, D.C. and was heading back to Chicago.

In a Friday morning statement, Emanuel described the mass shooting at Cornell Square Park in the 1800 block of West 51st Street in the city's Back of the Yards neighborhood as "senseless and brazen" violence that has "no place in Chicago and betray[s] all that we stand for."

"The perpetrators of this crime will be brought to justice and prosecuted to the full extent of the law," the statement continued. "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."

The shooting happened just after 10 p.m. Thursday when a gunman who witnesses say pulled up in a gray sedan and, along with a second shooter, opened fire on the park's basketball court. Four of the 13 victims were taken from the scene in critical condition, while the others were listed in serious or fair condition.

In a Friday morning press conference, Police Superintendent Garry McCarthy said police "believe the weapon used in this incident was an assault-style rifle with a high-capacity magazine." He added that he is in "constant contact" with the mayor concerning the incident and that he is "confident we're going to come to a quick conclusion on this, as we have on other high-profile" shootings in the city.

"This is something that we can't accept as OK in a civilized society," McCarthy added.

Chicago's top cop also noted all the victims' injuries are "non-life-threatening," describing it as a "miracle" that no fatalities are expected.

According to DNAinfo Chicago, the toddler injured critically in the shooting -- 3-year-old Deonta' Howard -- was listed in stable condition at Mount Sinai Hospital as of 7:30 a.m. Friday.

"It needs to stop," Semehca Nunn, Deonta's grandmother, told NBC Chicago. Nunn told the station her son was killed in a shooting last year.

Also wounded in the shooting were two minors -- a 15-year-old boy and a 17-year-old girl -- and the remaining victims ranged in age from 23 to 41, DNAinfo reports.

Witnesses say the gunmen fired at least 20 shots.

"I think it was like an AK," one neighbor told the Chicago Tribune of the shooting. "Man, it was a lot of shots. Man, boom, boom, boom, boom, boom."

Chicago police have said they believe the shooting was gang-related but have released little additional information as their investigation continues as of late Friday morning.

Emanuel was to speak at a Jersey City, N.J. rally for Senate candidate Cory Booker Friday afternoon.

Rev. Corey Brooks of New Beginnings Church told CBS Chicago he hoped the city will come together in response to the shooting to help prevent future violence.

“A lot of people in the city of Chicago have been desensitized towards the violence, and because of that, we’re really lax as far as it relates to trying to do something about it," Brooks told the station.

In other gun violence Thursday night into early Friday, two men -- 25-year-old Rubin Austin and 36-year-old Johnny Tinsey -- were fatally shot in separate incidents in Chicago, DNAinfo reports.

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  • Pictures of the suspects charged in last Thursday's mass shooting at Cornell Square Park are put on display during a press conference at police headquarters on September 24, 2013 in Chicago, Illinois. The four men charged are Kewane Gatewood, 20, Bryon Champ, 21, Brad Jett, 22, and Tabari Young, 22. Police believe the shooting was carried out in retaliation for an unreported shooting earlier in the day when Champ received a graze wound. (Photo by Scott Olson/Getty Images)

  • In this Thursday, Sept. 19, 2013, photo, a women becomes emotional near the scene of a shooting at Cornell Square Park in Chicago's Back of the Yard neighborhood that left multiple victims including a 3-year-old boy. Thursday night's attack was the latest violence in a city that has struggled to stop such shootings by increasing police patrols. (AP Photo/Sun-Times Media, Chandler West)

  • In this Thursday, Sept. 19, 2013, photo, bystanders convene near the scene of a shooting at Cornell Square Park in Chicago's Back of the Yard neighborhood that left multiple victims including a 3-year-old boy. Thursday night's attack was the latest violence in a city that has struggled to stop such shootings by increasing police patrols. (AP Photo/Sun-Times Media, Chandler West)

  • Twenty-six-year-old Cleo Miller hangs from the rim while playing basketball in Cornell Square Park Friday, Sept. 20, 2013, in Chicago. The park was the scene of a late-night attack Thursday, Sept. 19, 2013, in which 13 people were wounded, including a 3-year-old, by a gunman that used an assault-style weapon to spray the crowd with bullets, making it "a miracle" no one was killed, the city's police superintendent said Friday. The attack happened shortly after 10 p.m. while the Cornell Square Park was still crowded with people watching a basketball game and enjoying a warm late summer night. Investigators believe several people took part in the attack but weren't sure yet how many fired shots. (AP Photo/M. Spencer Green)

  • Morris Shadrach Davis, speaks outside his home on the west side of Chicago Friday, Sept. 20, 2013, about the shooting that injured his 3 year-old grand-nephew, Deonta Howard. The the child was injured during a shooting in the city's Cornell Square Park the night before. The park was the scene of a late-night attack Thursday, Sept. 19, 2013, in which 13 people were wounded, including 3-year-old, Howard. Police sources say the gunman used an assault-style weapon to spray the crowd with bullets, making it "a miracle" no one was killed, the city's police superintendent said. The attack happened shortly after 10 p.m. while the Cornell Square Park was still crowded with people watching a basketball game and enjoying a warm late summer night. Investigators believe several people took part in the attack but weren't sure yet how many fired shots. (AP Photo/M. Spencer Green)

  • This family handout photo provided by Rev. Corey Brooks shows 3-year-old Deonta Howard with his mother, Shamarah Leggett, recovering from a gunshot wound Monday, Sept. 23, 2013 at Mt. Sinai Hospital in Chicago. Howard was among 13 people shot Thursday night, Sept. 19, 2013, at Cornell Square Park on Chicago's southwest side. (AP Photo/Family photo via Rev. Corey Brooks)

  • This family handout photo provided by Rev. Corey Brooks shows 3-year-old Deonta Howard recovering from a gunshot wound Monday, Sept. 23, 2013 at Mt. Sinai Hospital in Chicago. Howard was among 13 people shot Thursday night, Sept. 19, 2013, at Cornell Square Park on Chicago's southwest side. (AP Photo/Family photo via Rev. Corey Brooks)

  • This family handout photo provided by Rev. Corey Brooks shows 3-year-old Deonta Howard recovering from a gunshot wound Monday, Sept. 23, 2013 at Mt. Sinai Hospital in Chicago. Howard was among 13 people shot Thursday night, Sept. 19, 2013, at Cornell Square Park on Chicago's southwest side. (AP Photo/Family photo via Rev. Corey Brooks)

  • Garry McCarthy

    Chicago police Superintendent Garry McCarthy speaks at a news conference Friday, Sept. 20, 2013, in Chicago. McCarthy discussed a shooting that occurred the night before in Cornell Square Park on the city's southwest side, that was the scene of a late-night attack Thursday, Sept. 19, 2013, in which 13 people were wounded, including a 3-year-old. The gunman used an assault-style weapon to spray the crowd with bullets, making it "a miracle" no one was killed, McCarthy said. The attack happened shortly after 10 p.m. while the Cornell Square Park was still crowded with people watching a basketball game and enjoying a warm late summer night. McCarthy said that based on witness interviews, it appears the attack was gang-related and that several victims are gang members. (AP Photo/M. Spencer Green)

  • This still frame made from Thursday, Sept. 19, 2013, video provided by Ken Herzlich, shows the scene where a number of people, including a 3-year-old child, were shot Thursday night in a city park in Chicago. Thursday night's attack was the latest violence in a city that has struggled to stop such shootings by increasing police patrols. (AP Photo/Courtesy Ken Herzlich)

  • Chicago Police detectives investigate the scene where 13 people, including a 3-year-old child, were shot in a city park on the south side of Chicago, Thursday, Sept. 19, 2013. Authorities said no one has been taken into custody in connection with the shooting. (AP Photo/Paul Beaty)

  • Chicago Police detectives investigate the scene where 13 people, including a 3-year-old child, were shot in a city park on the south side of Chicago, Thursday, Sept. 19, 2013. Authorities said no one has been taken into custody in connection with the shooting. (AP Photo/Paul Beaty)

  • The Chicago Fire Department hoses down the scene where 13 people, including a 3-year-old child, were shot in a city park on the south side of Chicago, Thursday, Sept. 19, 2013. Authorities said no one has been taken into custody in connection with the shooting. (AP Photo/Paul Beaty)

  • A Chicago Police detective collects crime scene tape from the scene where 13 people were shot, including a 3-year-old child, in a city park on the south side of Chicago, Thursday, Sept. 19, 2013. Authorities said no one has been taken into custody in connection with the shooting. (AP Photo/Paul Beaty)

  • A Chicago Police detective investigates the scene where 13 people, including a 3-year-old child, were shot in a city park on the south side of Chicago, Thursday, Sept. 19, 2013. Authorities said no one has been taken into custody in connection with the shooting. (AP Photo/Paul Beaty)

  • The crime scene where 13 people, including a 3-year-old child, were shot in a city park on the south side of Chicago, Thursday, Sept. 19, 2013. (AP Photo/Paul Beaty)

  • A Chicago police officer picks through debris at the crime scene where a number of people were shot, including a 3-year-old child, in a city park on the south side of Chicago, Thursday, Sept. 19, 2013. Chicago Fire Department officials said the child was in critical condition. Two other victims were also in critical condition. The others were reported in serious to fair condition. (AP Photo/Paul Beaty)

  • Map locates Back of the Yards neighborhood in Chicago, Ill.; 2c x 5 inches; 96.3 mm x 127 mm;

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