Catherine Benyamin's death has been ruled a homicide. An autopsy performed Friday found she had been strangled.
Police said are searching for the child's father, 37-year-old Jermaine Powell, to question him.
Joshua Powell was dropped off at a church near South Halsted Street and West Roosevelt Road in Chicago's University Village neighborhood around 7 p.m. Thursday, by a man matching his father's description.
The baby was taken to UIC Hospital to get checked out. He is now with Benyamin's sister and doing OK, though they are all seeking soothing and understanding.
"He wants his mom," said Cindy Benyamin as she tried to calm her nephew. "He wants his mom."
Her family said she didn't deserve to be killed, and that her life was just getting started. Her sister Claudia pleaded with Jermaine to turn himself in.
"I just want to know what happened, because I know you loved her and I know you loved Josh so much, and now he's lost both of you and I just want to know why," she said
Joshua was reported missing after officers found Benyamin, 31, dead in their home in the 8200-block of Keating Avenue in Skokie. A family member concerned about Benyamin's well-being had asked police to check on her.
Nicola Brown-Porter, a neighbor, was shocked to hear news of Benyamin's death.
"I'm very scared because my son is home by himself and it is very scary. I have a nine-year-old daughter and a 15-year-old son. It's very scary. I don't know what's going on in my building," Brown-Porter said.
"This is kind of surprising to me 'cause this is a really quiet neighborhood. No fuss, no fight, nor anything," said Claudette Haylett, who lives nearby.
Investigators said Benyamin's death was an isolated incident.