According to records from the medical examiner's office, the body was found in the trunk of a car.
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At least one person is in custody.
A 1-month-old girl was found alive inside the same house on Bo Jack Drive, where officers and agents from the Texas Rangers, Department of Public Safety, FBI and the Austin Police Department searched for hours overnight.
An ambulance took the baby to the hospital. According to Cy-Fair Volunteer Fire Department, she didn't have any obvious injuries, but Child Protective Services called in requesting an evaluation.
The baby was identified as Broussard's daughter, Margot Carey.
According to the medical examiner's office, Broussard's cause of death was ligature strangulation.
Investigators told ABC News they feared foul play from the start because one child was missing and one was left behind. Officials said the presumption is that if a mother were to run away voluntarily, she would either take both children or leave both behind. This particular situation was suspicious immediately.
Later Friday, Broussard's friend, Magen Rose Fieramusca, was charged with kidnapping in connection with her death.
The Harris County District Clerk website shows Fieramusca is being held in jail on three holds placed by the Austin Police Department: two kidnapping offenses and one tampering with evidence, a human corpse.
Friday evening, her bond was set for the charges, totaling $600,000.
TIMELINE: What we know about missing Austin mom and her 1-month-old baby
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At one point Thursday, ABC13 counted about two dozen officers and agents at the home.
An Eyewitness News crew waited for what was believed to be a warrant service. Then, around 8:15 p.m., there was movement, with law enforcement going into the house.
But authorities seemed to be more focused on a car in the driveway in the back. SkyEye13 was overhead earlier in the day, and a Nissan was seen parked up close to the house.
Through online records and a source, we learned the car investigators were interested in is registered to Fieramusca.
A neighbor told ABC13 police asked her Thursday night whether she remembers any movement here on that day. The only official response from the FBI is a vague statement: "The FBI is lawfully present at the location conducting a law enforcement operation."
Broussard and her infant daughter hadn't been seen since Dec. 12. That morning, Broussard dropped off her 6-year-old son at school. She then returned home and wasn't seen again.
Her car was left in the apartment parking lot, and she left her purse, ID and the baby's diaper bag.
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FBI Houston tweeted Friday morning that it has handed the investigation over to Austin police.
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