Gabby Petito was killed by another person, a coroner concluded while also confirming that the human remains found recently at a Wyoming national park were those of the 22-year-old woman who disappeared months after she set out on a cross-country road trip with her boyfriend, the FBI said Tuesday.Teton County Coroner Brent Blue determined Petito was a homicide victim, but did not disclose a cause of death pending final autopsy results, officials said. Her body was found Sunday near an undeveloped camping area in remote northern Wyoming along the border of Grand Teton National Park.Meanwhile, authorities continue to search a swampy Florida preserve area near the home of Petito's boyfriend. Police in North Port, Florida, said Tuesday morning that investigators have returned to the Carlton Reserve to look for Brian Laundrie, 23.Investigators searched the 24,000-acre (9,700-hectare) Florida nature preserve over the weekend without success. They focused on the area after Laundrie's parents told police he may have gone there.Authorities are using helicopters, drones, dogs and officers in all-terrain vehicles in their search for Laundrie. About 75% of the search area is underwater.On Monday, the FBI went to Laundrie's parents' home in North Port and removed several boxes and towed away a car neighbors said Laundrie's mother typically used.Laundrie and Petito had been living with his parents at the North Port home before the road trip on which she died.SEE MORE: 22-Year-Old Never Returned From Road Trip With Her FiancThe young couple had set out in July in a converted van to visit national parks in the West. They got into a fight along the way, and Laundrie was alone when he returned in the van to his parents' home Sept. 1, police said.Laundrie has been named a person of interest in the case, but his whereabouts in recent days were unknown.Petito's father, Joseph, posted on social media an image of a broken heart above a picture of his daughter, with the message: "She touched the world."In an interview broadcast Monday on TV's "Dr. Phil" show, Joseph Petito said Laundrie and his daughter had dated for 2 1/2 years, and Laundrie was "always respectful." During the interview, which was recorded before his daughter's body was found, Petito said the couple had taken a previous road trip to California in her car and there were no problems.Joseph Petito said the family began worrying after several days without hearing from their daughter."We called Brian, we called the mom, we called the dad, we called the sister, we called every number that we could find," Joseph Petito said. "No phone calls were picked up, no text messages were returned."Joseph Petito said he wants Laundrie to be held accountable for whatever part he played in his daughter's disappearance, along with his family for protecting him."I hope they get what's coming, and that includes his folks," Joseph Petito said. "Because I'll tell you, right now, they are just as complicit, in my book."The FBI said investigators are seeking information from anyone who may have seen the couple around Grand Teton.Gabby Petito and Laundrie were childhood sweethearts who met while growing up on New York's Long Island. His parents later moved to North Port, about 35 miles (55 kilometers) south of Sarasota.A man who saw Petito and Laundrie fighting in Moab, Utah, on Aug. 12 called 911 to report a domestic violence incident, according to a recording of the call obtained from the Grand County Sheriff's Office. The man said he saw Laundrie slap Petito while walking through the town and proceeded to hit her before the two got in their van and drove off.Video released by the Moab police showed that an officer pulled the couple's van over on the same day after it was seen speeding and hitting a curb near Arches National Park. The body-camera footage showed an upset Petito.Laundrie said on the video that the couple had gotten into a scuffle after he climbed into the van with dirty feet. He said he did not want to pursue a domestic violence charge against Petito, who officers decided was the aggressor.Moab police separated the couple for the night, with Laundrie checking into a motel and Petito remaining with the van.In the footage, Gabby Petito cried as she told the officer she and Laundrie had been arguing over her excessive cleaning of the van. She told the officer she has OCD obsessive compulsive disorder.On "Dr. Phil," her father said that was not literally true. She just likes to keep her living area orderly and was using slang, he said.Additional reporting by The Associated Press.