Brian Laundrie, the fiancé of Gabby Petito, has been missing for almost a week.
(CNN) -- Before Gabby Petito disappeared while on a cross-country van trip with her fiancé, her conversations with her mother appeared to reveal Petito had "more and more tension" with her travel partner, a police affidavit for a search warrant indicates.
The affidavit, filed by Florida police last week, offers new insight into what investigators have gleaned as they try to determine not only what happened to Petito but also the current whereabouts of the fiancé who returned to Florida this month without her.
Human remains that officials said are consistent with Petito's description were found Sunday in an undeveloped camping area in Wyoming's Bridger-Teton National Forest on the eastern edge of Grand Teton National Park. An autopsy is scheduled for Tuesday to confirm the identity.
Petito, 22, and Brian Laundrie, 23, had been road-tripping in a white van from New York through the US West over the summer, regularly posting photos and stories to their social media pages with the hashtag #vanlife.
Those posts abruptly stopped in late August, and Laundrie returned to his North Port, Florida, home on September 1 in their van without Petito, whose family reported her missing September 11. Authorities are looking for Laundrie, whose parents told investigators he left home with a backpack September 14, and have searched his home, including on Monday.
The case has become an obsession for many, spurring digital detectives to comb through the couple's online trail. The story has also further highlighted the tens of thousands of unsolved missing persons stories.
Before she vanished, Petito sent multiple text messages and had many talks with her mother via cell phone during her trip, Florida police wrote in an application filed last week for a search warrant for an external hard drive found in the couple's van.
In those conversations, there "appeared to be more and more tension between her and Laundrie," the affidavit reads. On August 27, Petito's mother received one last communication from her daughter, which she called an "odd text," the affidavit says.
The message read: "Can you help Stan, I just keep getting his voicemails and missed calls." Because the text message referred to Petito's grandfather as Stan, her mother was concerned that something was wrong, the warrant states.
Following that text message, Petito's phone was no longer operational and she stopped posting anything on social media about their trip, the warrant says.
One more text came on August 30 that read, "No service in Yosemite," but her family doubts she wrote it, Richard Stafford, an attorney representing Joseph Petito and her mother, Nicole Schmidt said.
Other evidence of tension between Petito and Laundrie also has emerged. A 911 audio recording in Utah sheds new light on a now-well-publicized incident in which police confronted the pair on August 12.
In the 911 recording from the Grand County Sheriff's Office in Moab, Utah, a caller reports what he called a "domestic dispute" between a couple.
"We drove by and the gentleman was slapping the girl," the caller says. "Then we stopped. They ran up and down the sidewalk. He proceeded to hit her, hopped in the car, and they drove off."
Police later stopped the couple, and previously released police documents and body-camera video reveal what followed that day.
Although the Petito and Laundrie are described in a police report as getting into a physical fight following an argument, "both the male and female reported they are in love and engaged to be married and desperately didn't wish to see anyone charged with a crime," Officer Eric Pratt wrote in the report.
At the suggestion by police, the couple separated for the night, the report said, which described Petito as "confused and emotional."
FBI searches Laundrie's home
The FBI on Monday searched the North Port home of Laundrie and his parents, removing many items over several hours.
An autopsy of the remains authorities discovered in the Bridger-Teton National Forest that may belong to Gabby Petito will be completed Tuesday.
Laundrie's parents, Christopher and Roberta, were escorted from their home Monday morning so agents could execute a search warrant, North Port police spokesman Joshua Taylor told CNN. They were later taken back inside for questioning.
His parents had previously told police that they had not seen Laundrie since September 14, which launched a search for him that initially centered on a nearby nature reserve.
The search for him will resume there Tuesday, North Port police said.
An attorney for Laundrie's family, Steven P. Bertolino, said he would also hold a news conference Tuesday, but later canceled the event. He said the FBI requested he not hold the conference.
Agents removed a number of items from the home, and a Ford Mustang convertible was also towed away.
'She touched the world,' father says
Pathologists will conduct a full forensic examination of the remains found Sunday to confirm the identity, said Charles Jones, FBI Denver's supervisory senior resident agent in Wyoming. Authorities also must identify the cause of death, he said.
Petito's family has been notified of the discovery.
Her father, Joseph Petito, tweeted a picture of his daughter Sunday evening, saying, "She touched the world." Richard Stafford, an attorney representing Joseph Petito and her mother, Nicole Schmidt, asked that the family be given space, per a statement obtained by CNN affiliate WABC.
Laundrie family attorney Steven Bertolino called the news "heartbreaking," adding, "The Laundrie family prays for Gabby and her family."
Laundrie's sister praised Petito for her relationship with Laundrie's nephews, according to a statement to ABC News.
"Gabby was a fun and loving influence to 'the boys' as she always referred to them. We will cherish the time we spent with her," Cassie Laundrie said.
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