Brian Laundrie argued in Wyoming restaurant hours before Gabby Petito vanished: eyewitnesses

Gabby Petito homicide: Timeline of disappearance & death

As we await an official cause of death on Gabby Petito, LiveNOW takes a look at some of the events leading up to where we are now. Investigators continue to comb the Florida wilderness for any signs of Petito's fiance, Brian Laundrie, who remains a person of interest in the case. Petito's death has been called a homicide, but how she was killed remains a mystery.

One of the last times Gabby Petito was seen alive involved an explosive argument between Brian Laundrie and wait staff at a Jackson Hole restaurant, according to a New Orleans couple who said they witnessed the spat.

"I have chills right now," Nina Celie Angelo told Fox News Digital Wednesday. "It's crazy because it wasn't just like we passed them on the street — it was a full blown incident."

Angelo said she and her boyfriend, Matthew England, were in town for a wedding in late August. They were out to lunch at Merry Piglets, a Tex-Mex restaurant, between 1 and 2 p.m. on Aug. 27, when they said an agitated Laundrie began arguing with a waitress. Four and a half hours later, a travel-blogging couple passed Petito's van at a campsite north of town.

Angelo, a photographer, said she couldn’t overhear the conversation but that she believed Laundrie was arguing with staff over the bill or about money. She described his body language as "aggressive" and said he left and returned about four times.

At one point, Petito came inside and apologized for Laundrie’s behavior, Angelo said.

A manager at the restaurant told Fox News that the business is "super busy during summer" and couldn’t recall the incident. Local police and the sheriff’s department deferred questions to the FBI, which declined to comment.

Angelo, who posted a detailed account of the scene on her Instagram, said she didn’t think much of the incident at first, and when they flew home to New Orleans, Hurricane Ida hit and upended their lives.

But after Utah police bodycam video emerged last week, her boyfriend, England, a financial adviser, connected the dots and realized that the couple arguing was Petito and Laundrie.

"He goes, ‘Nina, that was the couple fighting at the restaurant,’" Angelo said. "And it stopped me in my tracks. I felt like the blood left my body. I was like, ‘Oh my God, I completely forgot about that incident.’"

England told Fox News that he reported the incident to the FBI and that Petito appeared "visibly upset" with Laundrie as he hounded staff at the Merry Piglets Tex-Mex restaurant.

The incident happened roughly two weeks after Fox News Digital was first to report that a witness called 911 about a confrontation between Petito and Laundrie in Moab, Utah. Angelo and England said bodycam video of the police response matched the mannerisms and body language of Petito and Laundrie they witnessed firsthand. Laundrie was also wearing clothes England said he recognized from the video and "looked kind of like he had been living out in a van for a little while."

"I spent the last three or four days really kind of racking my brain," he told Fox News Wednesday. "And I woke up this morning and went to Facebook, and there was that video with the police on it right away. That was the couple."

Then it clicked.

"I would bet $10 million, I’m 1,000% sure that was him and that was her," he said.

England also provided a credit card statement showing he spent $60.88 at the restaurant Aug. 27.

Angelo said it did not appear that Laundrie was on drugs, and he was "not screaming." But he was behaving aggressively with the restaurant staff, a waitress, a hostess and the manager – all women.

Aug. 27 is around the time Petito last made contact with friends and family. On Sept. 1, Laundrie is believed to have arrived at his parents’ home in Florida without her, driving her van.

The FBI said her remains were discovered Sunday at a campsite north of Jackson Hole.

Get updates on this story at FOXNews.com.