Lavontay White, identified by the Cook County Medical Examiner's office, was later pronounced dead in hospital.
The 11-year-old, Takiya Holmes, who was shot while sitting in her mother's auto, succumbed to her injuries earlier on Tuesday. She was wounded in the stomach, and was listed in fair condition.
No one is in custody for the shooting, which occurred in broad daylight and was streamed on Facebook Live by one of the victims, police said.
"We have very promising leads", Johnson said at a news conference.
The video, streamed live on Facebook, was taken from inside a vehicle driven by a young woman who was wounded in the shooting.
Jones spotted three people outside his home, determined they didn't belong there and went inside and got a handgun, police said.
"Every parent, regardless of where they live, should be able to take their child for a walk to the park or a ride in the vehicle", he said. Police claim that the man who died was a known gang member.
Levontay was the second child to die on Tuesday from gun violence in Chicago.
Police say they have a good idea about the identity of the shooter. The injured woman then is heard to state "I got a bullet in my stomach ..." The man was also shot in the head. On the first day of January alone, 28 people were shot in Chicago, according to data from the Chicago Police Department. The toddler is believed to be 2 or 3 years old. The shooting comes just days after two girls, ages 11 and 12, were both shot in the head in separate unrelated shootings that took place within 25 minutes of each other over the weekend in Chicago. The woman is in critical condition.
"They just don't fear it, and until we create that mental accountability to them to not pick up a gun, we're going to continue to see this cycle of violence", Mr Johnson said.
About 11:55 a.m., a 23-year-old man was fatally shot in the 2000 block of East 71st Street in the South Shore neighborhood, according to police.