Although the body has not been formally identified, family members confirmed to news outlets it is that of the missing 33-year-old.
Two people were arrested, and according to KHOU, a woman is to be charged with murder imminently. She has also been charged with kidnapping and evidence tampering. Her bond is set at $600,000.
The discovery was made after a citizen made a call to Child Protective Services; dozens of officers from the Texas Rangers, Texas Department of Public Safety, FBI and Austin Police Department descended on the address.
Police sources told KVUE that the suspect is a "close friend" of Broussard's, who was with her when she gave birth to Margot. They said she had been pretending to be pregnant herself, and had been plotting to kidnap the baby.
Heidi was last seen dropping her six-year-old son Silas off at school last Thursday last week.
Heidi's fiance Shane Carey said she had called him at 8am to tell him she bought books at a book fair; he tried calling her back at 1.40pm but her phone went straight to voicemail.
When he returned home from work at 2pm he expected her to be there with their daughter, but they weren't there.
Her car was parked outside, unlocked, with her purse, ID and bank cards all intact. The only things missing, he said, were her keys and cellphone. He then got a call from the school to report nobody had picked up Silas. After picking up the boy, he notified police.
Last week, Carey made emotional pleas for their return through local media.
"I don't know why anybody would ever harm or touch these two beautiful women together," he said. "She would not do this by herself. She would not be doing this. This is definitely something that happened that was wrong."
"She is an amazing person. She has amazing support, friends behind her. She's so personable – one of the best people I've ever met, so kind, and she does anything for her kids – one of the best moms."