Police said he punched the 23-month-old boy multiple times in the face around 12:11 p.m. on the 4200 block of South Calumet Avenue.
According to police, the adult male suspect has unspecified mental illness and was taken into custody at the scene. The child was pronounced dead at Comer Children’s Hospital.
Charges are pending, a Chicago Police Department spokesman told Fox News.
Police described the incident as a domestic situation and said the investigation was ongoing with Area One detectives. The suspect's identity was not released.
Chicago has seen a surge in violence in recent weeks, including the deaths of at least four other children under 10 years old, according to CBS Chicago. Those have been attributed to gun violence, specifically.
One of the victims was a 7-year-old girl named Natalia Wallace, who was shot and killed while playing outside her grandmother’s house on Independence Day.
“Thoughts and prayers are simply not enough at this point,” Mayor Lori Lightfoot said of Natalia’s death Monday. “Sorrow itself is not enough. What it says is we need to do better as a city.”
There were at least 17 people killed by gunfire over the Fourth of July holiday weekend alone, including multiple children. Another 70 were wounded.
Chicago Police Superintendent David Brown wrote an op-ed published in the Chicago Tribune on Monday, calling on city residents to come together with police, the government and the courts to make the city’s streets safer.
“We cannot expect community members to turn criminals over to the police if they know that our criminal justice system will return most of those criminals right back to the street,” he wrote.