(CNN) Marlen Ochoa-Lopez attended her classes at Latino Youth High School last month and planned to pick up her 3-year-old at day care later that afternoon.

But first, the 19-year-old, who was nine months pregnant, stopped by a home in Chicago to pick up some baby items, police said.

That was on April 23, the last day she was seen alive. Her body was found Tuesday in a garbage can in the backyard of the woman who'd offered her the baby supplies, police said.

Ochoa-Lopez had been strangled with a cable, and her unborn baby forcibly removed from her womb, Deputy Chief of Detectives Brendan Deenihan said. The baby boy is hospitalized in grave condition.

An appeal for a baby stroller

Before Ochoa-Lopez went missing, she appealed to mothers on a Facebook group called "Help A Sister Out." She needed a double stroller for her toddler and the baby on the way, according to the posts.

The high school student wrote that she was jobless and short on cash, and was willing to buy, trade or simply accept a donation.

A woman responded with an offer of new baby clothes and other unused items, and asked Ochoa-Lopez to message her privately. Ochoa-Lopez had bought other baby items from her in the past, police said.

Clarisa Figueroa, 46, Desiree Figueroa, 24, and Piotr Bobak, 40.

The woman, Clarisa Figueroa, 46, and her daughter, Desiree Figueroa, 24, were charged Thursday with first-degree murder and aggravated battery of a child less than 13 years old, police said.

The three suspects are due in court Friday, Figueroa's boyfriend, Piotr Bobak, has been charged with concealing the death of a person and one felony count of concealing a homicidal death.The three suspects are due in court Friday, CNN affiliate WGN reported.

"Words really cannot express how disgusting and thoroughly disturbing these allegations are," Chicago Police Superintendent Eddie Johnson said.

An agonizing search for answers

Ochoa-Lopez's anguished relatives searched for her for three weeks.

Her husband tried to immediately report her missing to the police, but was told to come back in 72 hours, according to the family's pastor, Jacobita Cortes. He did and the family hired a private investigator, who Cortes said helped find Ochoa-Lopez's car near the home where her body was found.

They also turned to the local church for help in reaching out to the community at large, plastering the neighborhood with missing persons fliers.

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.

Ochoa-Lopez's father, Arnulfo Ochoa, said there were opportunities to find his daughter sooner.

Marlen Ochoa-Lopez's family speaks to the media Thursday.

"(The private detective) went into that (Facebook) page and found all the information, and he gave it to the police. But even then, they took too long to get there," Ochoa said at a news conference Thursday.

The same day Ochoa-Lopez went missing, the Chicago Fire Department received a call about a newborn in distress at the home where her body was eventually found, authorities said.

For the three weeks she was missing, Ochoa-Lopez's baby boy had already been forcibly removed from her womb and was hospitalized along with a woman who claimed to be his mother, according to fire department spokesman Larry Langford.

"There's going to be anger associated," Johnson told reporters. "When things of this nature occur, the first thing people do is look in retrospect, what could we have done to maybe prevent this? I know our detectives do the best they can."

A break in the case

The break in the case came May 7, police said.

A friend of the victim told detectives about her Facebook exchanges with Figueroa before she vanished. But Ochoa-Lopez's family said they notified authorities about her interaction with the woman much sooner.

Detectives visited the Figueroa home last week after learning of the Facebook contact between the two women.

Desiree Figueroa told them her mother was in the hospital for problems with her legs. Then she revealed that her mother had just delivered a baby, authorities said.

When investigators interviewed the elder Figueroa, she denied the victim came to her house on April 23 but she admitted to meeting her in the past.

Suspicious, detectives subpoenaed hospital records and began to collect DNA samples from the baby, his biological father and Figueroa.

The DNA matched the baby's father, said Cortes of Adalberto Memorial United Methodist Church.

A confession and questions

On Tuesday, armed with a search warrant, crime lab officers searched the house.

Detectives discovered bleach and cleaning solutions in the home, along with evidence of burned clothing and blood on the floors of the living room, bathroom and a hallway, according to Deenihan.

"They are finding remains of burned clothes, they are finding some blood indication on the living room carpet, some blood indication on the hallway, some blood indication on the bathroom floor," police said.

Ochoa-Lopez's body was found in a garbage can in the yard, along with the cable used to strangle her and other evidence. Desiree Figueroa told detectives she helped her mother strangle her, police said.

The motive for the killing is under investigation, but the superintendent said he believes the suspect wanted to raise the child as her own. Figueroa lost a son who was in his 20s to natural causes in 2017.

Ochoa-Lopez's mother, Raquel Uriostegui, broke down after identifying her body.

"I want justice for my daughter, my only daughter," she said. "This can't stay like this."