One by one, a woman stabbed her five children and then her husband, killing all but one daughter inside a Gwinnett County mobile home. Then, Isabel Martinez called 911 to report what she’d done.

The day after her arrest, Martinez smiled and gave a "thumbs up" sign in a courtroom, telling a judge she didn't need a lawyer. Family members and neighbors said Martinez had mental health issues, and the death of her father had fueled a deep depression. But it still didn't explain Martinez's actions on July 6, 2017.

Within hours of officers’ arrival, Martinez was arrested and booked into the Gwinnett jail, where she has remained since. In a surprise announcement late Tuesday, the Gwinnett district attorney’s office said Martinez had pleaded guilty to the crimes and was sentenced to life in prison, with the possibility of parole.

Martinez, 35, entered guilty pleas to five counts of murder, one count of aggravated assault and one count of cruelty to children.

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Martinez’s defense attorney, Don Geary, told Channel 2 Action News she pleaded guilty, but mentally ill. Prosecutors were not available to comment late Tuesday.

On that July morning, investigators found the bodies of Martin Romero, 33, and four children: 2-year-old Axel, 4-year-old Dillan, 7-year-old Dacota and 10-year-old Isabela Martinez inside the family's home. A 9-year-old girl, Diana, was seriously injured but survived the attack. She would later recount the details to investigators, including how her mother told her she was "going to the sky to see Jesus."

Martinez initially claimed a “family friend” had killed her family, but she couldn’t provide a name. But little Diana told a different story.

<p>Isabel Martinez</p> <p>Isabel Martinez</p>

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Diana Romero told a Division of Family and Children Services worker that Martinez began stabbing the children first. When Martin Romero tried to stop her, Martinez stabbed him, according to a DFCS report. Martinez was not crying or screaming as she killed her family members, Diana told a DFCS worker.

The family had just returned from a trip to Savannah. After the killings, Martinez told a DFCS worker she felt a "devil-like spirit" was trying to take her children when they were playing in the ocean.

Hundreds attended the memorial service for the family, where a statement was read from other relatives.

“First, we would like to thank you all for the outpouring of support and the continuous prayers that have been given to our family through this unimaginable circumstance,” the statement read. “The love and kindness we have received from many has been a comfort for us in our time of grief.”

The DA's office announced last year it would not seek the death penalty against Martinez.

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In a small mobile home community in Gwinnett, Isabel Martinez was charged with multiple counts of murder in the stabbing deaths of four of her children and their father. (Erica A. Hernandez/AJC)