(CNN/CBS4) — 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.

Gabby Petito

Gabby Petito (credit: Instagram/GabsPetito)

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.

On Tuesday, FBI Denver announced the Teton County Coroner’s Office confirmed the remains found on Sunday at a dispersed camping site are of Gabby Petito. They add the coroner’s office has initially ruled the death a homicide, but the cause is still pending.

A police search for the fiancé, Brian Laundrie, resumed Tuesday at a Florida nature reserve where his parents reportedly said he indicated he was going last week.

Petito, 22, and 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.

(credit: Gabby Petito)

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, Nichole 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.”

A National Park Service ranger who also responded to the call interacted with Petito for about 90 minutes, and warned her that her relationship with Laundrie had markings of a “toxic” one, the ranger told the Deseret News of Utah.

“I was imploring with her to reevaluate the relationship, asking her if she was happy in the relationship with him, and basically saying this was an opportunity for her to find another path, to make a change in her life,” ranger Melissa Hulls told the Deseret News.

(credit: Gabby Petito)

CNN has sought comment from Hulls.

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.

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, when he told them he was going to the Carlton Reserve, a 25,000-acre nature reserve near Venice, Florida, according to authorities.

Investigators resumed their search there at 8 a.m. ET Tuesday, the Florida Fish and Wildlife Conservation Commission said.

North Port police on Tuesday announced they were resuming their search on the Venice side of the reserve after saying Monday they’d shifted their search away from the reserve, having “exhausted all avenues” there. Agents from the fish and wildlife commission were requested Monday afternoon, commission spokesperson Adam Brown said.

An attorney for Laundrie’s family, Steven P. Bertolino, said he would 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 Monday, and a Ford Mustang convertible was also towed away.

Before his parents told police Laundrie left the home September 14, he had refused to talk to investigators, and the family had directed them to their attorney, police said. Laundrie has not been charged in the case.

‘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, 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.

Correction: A previous version of this story misspelled the name of Petito’s mother, Nichole Schmidt.

By Jason Hanna, Madeline Holcombe and Leyla Santiago, CNN

© Copyright 2021 CBS Broadcasting Inc. All Rights Reserved. CNN contributed to this report.