Marlen Ochoa-Lopez was nine months pregnant when she went missing.
The dark-haired 19-year-old vanished on April 23, after she made an appeal to mothers on a Facebook group called "Help A Sister Out."
She needed help securing a double stroller for her toddler and a new baby on the way, according to social media posts and a pastor who has been assisting her family.
A student at Latino Youth High School, Ochoa-Lopez wrote that she was jobless and short on cash. She was willing to buy, trade or simply accept a donation.
A stranger responded with an offer of new baby clothes and other unused items, according to the posts. She asked Ochoa-Lopez to message her privately.
Ochoa-Lopez's body was found this week in a Chicago home, where police said she was strangled to death and her unborn baby forcibly removed from her womb. Three people who were in the home have been charged, two with murder and one with concealment of a crime, police said.
"The day before Marlen went missing, she gave her mother a big hug and told her, 'You're the best mom in the world,'" said Jacobita Cortes, a pastor at Adalberto Memorial United Methodist Church in Chicago, where the family has sought help.
"Her mother told me Marlen was always affectionate, but that day she seemed especially loving. And the next day Marlen disappeared."
On the day she disappeared, the Chicago Fire Department had received a call about a newborn in distress from the home where the young mother's body was eventually found, authorities said.
Three people charged
The baby, now in grave condition, was taken to a hospital that day along with a woman who claimed to be the mother, according to fire department spokesman Larry Langford.
But Ochoa-Lopez's family has received confirmation the newborn is her baby, Cortes said. Local media have also reported that Ochoa-Lopez is the baby's mother.
"We believe that she was murdered, and we believe that the baby was forcibly removed following that murder," Anthony Guglielmi, a Chicago police spokesman, said.
The identities of the three people charged in the case have not been released.
Police declined to confirm any other details, citing an open investigation.
Authorities asked for Ochoa-Lopez's dental records as well as a hairbrush and toothbrush from her family to identify her body, the pastor said. They also matched the baby's DNA to the father, she said.
"We lived together for four years and now I see her with her eyes closed," Yovany Lopez, standing outside the morgue in tears, told CNN affiliate WGBO. "Why would these people do this? She did nothing to them. She was a good person. How could they do this knowing she has family and a three-year-old son?"
Ochoa-Lopez's mother, Raquel Uriostegui, cried: "I want justice for my daughter, my only daughter. This cant stay like this."
Family mourns and prays
Ochoa-Lopez was last seen more than three weeks ago after leaving Latino Youth High School. She was supposed to pick up her 3-year-old from day care later but never showed up, authorities said.
Cortes, the pastor, said Ochoa-Lopez's husband tried to immediately report her missing to the police, but was told to come back in 72 hours. He did and then hired a private investigator, who Cortes said helped find Ochoa-Lopez's car near the home where her body was found.
He went to Cortes for help and plastered the neighborhood with missing persons fliers with Ochoa-Lopez's photo, the pastor said. Residents last week started calling the church to report that they had seen the young mother enter the house where she was found dead. They said that one of the women who lived there, in her 40s, suddenly had a baby without ever appearing to be pregnant, according to Cortes.
The pastor said the information was turned over to the police, but they did not enter the home and detain the residents until the forensic evidence established that Ochoa-Lopez was the mother. They later discovered her body.
As family members mourn the young woman, they are praying that the baby survives, the family's spokeswoman said.
"It just seems surreal. You see this stuff on the movies. You never get to know someone; people actually are this evil," a family spokeswoman, Cecilia Garcia, told CNN affiliate WGN.
CNN's Ray Sanchez, Melissa Alonso, Joe Sutton and Chris Boyette contributed to this report.