BAYTOWN, Texas – A woman found dead Wednesday inside a pickup truck in a Walmart parking lot was not a victim of homicide, investigators said.

After performing an autopsy, the medical examiner said Kara Lee Williams, 24, died from "inhaling the contents of multiple aerosol cans." Investigators said the cans were purchased in the hours prior to her death.

Williams was found sitting in a Toyota Tundra pickup truck and went unnoticed for two days. A shopper at the Walmart off Highway 146 and I-10 saw something suspicious and alerted a deputy patrolling the lot. Williams was discovered dead.

The pickup truck belongs to the father of Williams' boyfriend.

We talked with the boyfriend's father who said Williams, of Baytown, told his son she was going to babysit. His son called Williams but didn't hear from her for two days, according to his father.

At the time Williams was found, she was not wearing any pants , which lead investigators to believe she may have been sexually assaulted and killed.

Hawthorne said they determined she'd been there for two days because Walmart store surveillance video showed her leaving and getting into the truck. He said his son reported Williams missing Sunday.

"Approximately 1:20 in the morning on the 11th she was alive and walked out of Walmart," Hawthorne said.

Partially nude woman found dead in Wal Mart parking lot was here for two days. More details at 5 on @KPRC2 pic.twitter.com/rm3r5HZyM8 — Robert Arnold (@KPRC2Robert) April 13, 2016

"She stayed in the parking lot. She never left the parking lot," Hawthorne said.

The boyfriend's father said his son and Williams had been on and off for two years and moved to Baytown a week ago. They used the father's silver truck to move furniture to their new home, he said. The truck was at the center of the investigation Wednesday.

"I find it really crazy," shopper Perla Prieto said. "I don't know how no one could notice her."

The investigation is ongoing.