So far, the teenager, who is from Calumet Heights, has not been charged with the crime. Prosecutors are considering what charges he may face.
"We're reviewing the case right now, so I am not going to misspeak...there's someone in custody," said State's Attorney Anita Alvarez.
There are reports that the suspect was in a Joliet facility serving a four-year sentence for a similar crime that happened on May 15.
A Chicago police spokesperson tells ABC7 that "significant progress has been made in the case. The investigation is on-going as detectives continue to talk to witnesses. However, no charges are immediately anticipated."
Police say Katona-King was knocked down the stairs after someone robbed her of her iPhone at the CTA Red Line Fullerton stop. Her death was ruled a homicide.
At the Chicago Synod of the Evangelical Lutheran Church, where Katona-King worked as a receptionist, there is a sense of relief.
"The Christian faith is not interested specifically in punishment or exoneration. We're interested in the truth," said Bishop Wayne Miller, Chicago Synod of the Lutheran Church.
Bishop Miller says, with someone in custody, it's now about the criminal justice system.
"The best outcome is for the truth to come to the surface. If the person is guilty, then I think he should pay the consequences. If he is innocent, I hope the eagerness people have for closure doesn't press for an unjust verdict either," said Miller.
Katona-King, who was 68, was also a deacon at her neighborhood church, the First Lutheran Church of Logan Square. She lived nearby, and her neighbors miss her kind-hearted spirit.
"It was very good news this morning to hear that perhaps they have someone in custody," said Lauramarie Matijevic, neighbor.
At the Fullerton "L" Stop, riders want people held responsible, especially if they commit crimes.
"I'm just thankful, you know, just for the fact that, you know, we don't have to worry about someone looking to hurt other people," said Marcellus Ford, Red Line rider
"I think it's awesome that they finally, hopefully caught the guy because the poor lady didn't deserve that," said Jasmine Beltran.