A U.S. Marine reservist who disappeared in Mexico last month along with his father and uncle may have stumbled into an ongoing land dispute between his family and a neighbor, family members said Tuesday.

The FBI announced Monday it's looking for information about the May 14 disappearance of 25-year-old Iraq War veteran Armando Torres III of Hargill, Texas. He, his father, Armando Torres II, and uncle Salvador Torres were taken from the ranch in Mexico, not far from the border.

Patricia Torres, the reservist's aunt, said Tuesday that her father-in-law — Armando Torres Sr. — had sold a piece of his ranch in La Barranca, Tamaulipas, to a neighbor. When that neighbor stopped making payments on the land, Salvador Torres took it back.

"That's when everything started," Patricia Torres said from the porch of her nephew's trailer home. "That's when they said they were going to have revenge and that they were going to regret it. After a month passed by, this happened."

In addition to the criminal investigation by Mexican officials, the FBI has opened a concurrent international kidnapping investigation.

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Armando Torres III's sister Cristina Torres chatted online with her brother the day before he disappeared. She said he told her he wanted to move to Virginia where she and their mother live.

"I think maybe he just wanted, you know, to go and have a farewell and tell my dad he's coming over here," said Cristina Torres, 24, of Harrisonburg, Va. He hadn't traveled to Mexico in years, because, as a Marine, he was not allowed to cross the border, she said.

Patricia Torres said a woman picked him up on May 14; she thinks the woman was his ride to the international bridge at Progreso, Texas.

Between 8 and 9 p.m. on May 14, Cristina Torres received a call from her cousin in Mexico who was at another home on the property, in a small settlement near the end of the international bridge at Los Indios.

"Ten or 20 minutes after they got kidnapped, my cousin called me," she said. "She said that she saw a white truck just pull in and a couple men just got out of the truck and went inside the house and ambushed them and took them out and put them in the truck.

"She said that they were arguing back and forth until they got in the truck and they left."

The cousin also told Torres her father's home was robbed and all three men's vehicles were stolen.

Late that night, another uncle filed a report with the Hidalgo County Sheriff's Office. The report said that Armando Torres III had left for Mexico around 6 p.m. that evening. The uncle said he had tried calling his nephew's cellphone, but it went straight to voicemail.

"This is because of the property," Patricia Torres said. "But the persons that had the property were involved, I believe, with the cartel because they were the ones that picked them up."

Stories abound of the drug cartels forcefully taking ranches to facilitate their drug trafficking, and properties near the border are especially attractive. The segment of border where the ranch is located is an important drug trafficking corridor for the Gulf cartel.

Armando Torres III served with the U.S. Marines in Africa and Iraq, Cristina Torres said. He had been diagnosed with post-traumatic stress disorder and had struggled with anxiety and anger management, she said, but had gotten it under control with medication and treatment through the Department of Veterans Affairs.

Patricia Torres said the reservist had most recently been working for an energy services company. He has two sons, but is separated from his wife, Melissa Estrada.

Estrada said her husband had texted her the day he went to Mexico to say he was going out of town. He normally takes their sons for three or four days at time because they want to see him and she works and goes to school full-time.

He's a big help with his sons and had recently come out of a "funk" he had been in, she said. She was encouraging him to move to Virginia where he'd have more opportunities.

"There's no bad news, so that's still good," she said.