In the weeks before Gabrielle “Gabby” Petito disappeared during a road trip with her fiance, police responded to a call reporting a “domestic problem” between the couple.

According to a police report obtained by The Washington Post, a witness called 911 on Aug. 12 after he saw Petito, 22, and Brian Laundrie, 23, squabbling over a phone outside the Moonflower Community Cooperative — a natural-food store in Moab, Utah.

The onlooker, identified only as Christopher, said he saw Petito slap Laundrie during the argument. Christopher said Petito then climbed into the vehicle through the driver-side window “as if Brian had locked her out and she was trying to find a way in,” the police report said. Then, the couple drove away.

When Christopher saw the fight unfold, he told police he “feared the worst.”

Investigators in North Port, Fla., where Laundrie and Petito lived together, on Wednesday named Laundrie a person of interest in Petito’s disappearance. The North Port Police Department said in a statement that Laundrie had declined to share “any helpful details” and noted that he returned to Florida without Petito on Sept. 1.

Petito’s parents reported her missing 10 days later, police added.

“We are pleading with anyone, including Brian, to share information with us on her whereabouts in the past few weeks,” North Port Police Chief Todd Garrison said in a statement Wednesday. “The lack of information from Brian is hindering this investigation. The answers will eventually come out.”

An attorney for Laundrie said that he would not be providing any information about the case to the police.

“On the advice of counsel the Laundrie family is remaining in the background at this juncture and will have no further comment,” attorney Steven Bertolino said in a statement shared with The Post on Wednesday.

“This is understandably an extremely difficult time for both the Petito family and the Laundrie family,” Bertolino added. “It is our understanding that a search has been organized for Miss Petito in or near Grand Teton National Park in Wyoming. On behalf of the Laundrie family it is our hope that the search for Miss Petito is successful and that Miss Petito is re-united with her family.”

On Aug. 12, police caught up with Petito and Laundrie in their white 2012 Ford Transit van a few miles from the Moonflower co-op near the turnoff for Arches National Park, according to the report. When an officer turned his cruiser’s lights on to stop the van, Petito grabbed Laundrie’s arm to get his attention and caused the vehicle to swerve into the curb before it stopped, the report said.

The officer who pulled them over noted that Petito was “crying uncontrollably” in the passenger seat.

“At no point in my investigation did Gabrielle stop crying, breathing heavily, or compose a sentence without needing to wipe away tears, wipe her nose, or rub her knees with her hands,” one officer wrote in the police report.

Weeks of traveling together had created an “emotional strain” on their relationship, Laundrie told Moab police officer Daniel Scott Robbins. The close quarters had “increased the number of arguments” between the pair. Petito also told police she had been suffering from “serious anxiety.”

According to the report, Petito added that because of the “little arguments she and Brian had been having all day, she was struggling with her mental health.”

Laundrie told Robbins that Petito feared he would leave her in Moab without a ride, which spurred her “manic state” and caused the physical altercation between them. According to police, Petito left minor scratches on Laundrie’s face and right arm during the struggle.

Despite the fight, both Laundrie and Petito asked police to refrain from filing charges.

“Both the male and the female reported they are in love and engaged to be married and desperately didn’t wish to see anyone charged with a crime,” another officer, Eric Pratt, wrote in the police report.

Police said Laundrie had “no fear for his safety,” and the officers determined he was at “low risk of danger or harm” from Petito, in part because she was much smaller than him. Police also noted that no one reported Laundrie had harmed Petito in any way.

Instead of making an arrest, Robbins ordered Laundrie to stay in a hotel room provided through the city’s “Safe Haven” program for the night so that he and Petito could spend some time away from each other. Robbins drove Laundrie to the hotel and left Petito with the van for the night.

“I instructed both Brian and Gabrielle to take advantage of this time apart to relax their emotions and regain control of their anxiety,” Robbins wrote in the report.

Petito’s family issued a new statement Wednesday, WLNY reported, in which they called on Laundrie to answer questions about his fiancee’s disappearance. They referred to his silence as “reprehensible.”

“We beg you to do the right thing and help us bring Gabby home,” Petito’s family said, according to the station. “Brian, whatever happened in Wyoming, happened. The only thing you can control is what you do now. Tell us where Gabby is.”