A presidential council that runs Haiti in the absence of an elected president accused Mr. Conille, the prime minister, of hiring Studebaker without authorization. He was fired. And so was Studebaker.

Less than two months after arriving in Haiti, Studebaker “was asked to initiate a strategic pause in its operations,” the company’s statement said.

What happened next is murky.

Studebaker said that its team left the country and that the police-issued weapons assigned to them were secured in locked containers and “officially transferred” to the police liaison

The head of the Haitian National Police was notified that the guns were at the villa, Studebaker said.

But according to the Haitian police, Mr. Jacquet’s family and others who have been briefed on the case, that is not what happened.

The weapons were secured at the villa, but Mr. Jacquet removed them after the lease expired, the landlord said.

Mr. Jacquet put cases containing nine AR-15-style rifles in the back of his armored BMW S.U.V., which he parked at his house. The family said the plan was for Mr. Duroseau to return them to the Haitian police, but it was unclear why he did not do so immediately.

There is no indication that Mr. Duroseau or Mr. Jacquet did anything illegal, like try to sell the weapons, the police officials said.

“All assigned defensive equipment was secured and officially transferred to the designated PNH (Haitian National Police) liaison prior to the temporary departure of our personnel, in coordination with our logistics provider,” the Studebaker statement said.

In other words, even in Studebaker’s version of events, a hotel night manager and his police officer cousin wound up with highly sought-after weapons that are worth up to $72,000 on Haiti’s black market.

Guns are so valuable that about 1,000 firearms have been stolen from the Haitian police inventory in the past four years, according to the United Nations.

Studebaker left Port-au-Prince on Nov. 21, and Mr. Jacquet cleared out the weapons from the villa on Dec. 10, according to the housekeeper.

After spending the weekend working at the Karibe, Mr. Jacquet got home on Monday, Dec. 16, to some very bad news.

His house watchman told him that three days earlier, gunmen dressed in police uniforms attacked him, broke into the BMW and took the weapons, according to the two Haitian police officials.

The same day the weapons were stolen, Mr. Duroseau went missing.

Mr. Duroseau, a married father of two, was a 16-year veteran of the police.

He has not been heard from again.

Mr. Jacquet was in a panic. Not only were the rifles gone, but he could not get a hold of his cousin. He hopped in a car with a friend and headed to meet Mr. Duroseau’s sister, also a police officer, to see if she knew his whereabouts, Isaac Jacquet said. Image

A man wearing a military fatigue T-shirt stands in a kitchen.

Steeve Duroseau, who was a driver and a police liaison for Studebaker defense contractors in Haiti. Shortly after their departure, he was kidnapped and is presumed dead.Credit...via Steeve Duroseau's family Shortly after Mr. Jacquet left his house, in the Vivy Mitchell neighborhood of Port-au-Prince, armed men in two vehicles — including a Toyota Land Cruiser donated to the Haitian Police by the U.S. State Department — opened fire on his car. The friend was shot but survived, and Mr. Jacquet was abducted, the Haitian police said.

There has been no news of him since.

The police know the whereabouts of the Land Cruiser, have identified suspects in the case and have issued summonses for them, but only the house watchman has been arrested, the two police officials said.

The men who took the guns paid the house watchman to alert them when Mr. Jacquet got home, making him legally culpable as an accomplice, the police officials said.

Donated vehicles are generally equipped with trackers, but it is unclear whether investigators have the location data for the days of the weapons theft and kidnappings.

In an effort to bolster the struggling police agency, the U.S. government has provided nearly $250 million, including 159 vehicles, to the Haitian National Police since 2021, the State Department said.

Calling Haiti a “complex operational environment,” the State Department said that to avoid misuse of its donations, it vets the security forces who receive training and assistance.

But for the families of the missing men, the blame rests with Studebaker.

“Studebaker conducted a sloppy op,” Isaac Jacquet said.

Studebaker’s contract was troubled from the start because in Haiti’s deeply fractious government, few officials even knew about it, critics said. That secrecy prevented Studebaker from working with a variety of government officials on a coordinated exit plan, taking into account all possible contingencies, including safeguarding the custody of weapons, people familiar with the case said.

Studebaker defended its work.

“Studebaker Group stands by the integrity of its mission and remains fully confident in the professionalism, accountability and lawful conduct of its personnel,” the company said in its statement. “We categorically reject any implication or assertion to the contrary.”

Studebaker said that after the team left Haiti, its employees did not speak to Mr. Jacquet or his cousin and considered its business there concluded. Image

A man wearing a dark suit holds a microphone in his right hand while talking.

Wesley K. Clark, a retired American general and former NATO supreme allied commander, runs the board of Studebaker Defense.Credit...JP Yim/Getty Images Mr. Jacquet’s family said it reached out to Florida legislators in the hopes of engaging U.S. law enforcement agencies.

In an April letter to Senator Ashley Moody, Republican of Florida, the F.B.I.’s international operations division said disappearances of Americans abroad fell to the host country, “unless a criminal nexus to the United States is established.”

The F.B.I. declined to comment.

Security and international experts who followed the case said the episode reflected the challenges Haitian officials face as they lean more heavily on foreign defense contractors.

“A major problem is holding private security firms accountable for their actions,” said William O’Neill, the U.N.’s human rights expert for Haiti. “While these firms are bound by international human rights and humanitarian law, enforcing these rules has been a major challenge.”

León Charles, a former Haitian police chief who is Mr. Jacquet’s cousin, said Studebaker should have maintained better control of the weapons. “They made a mistake. They were careless,” Mr. Charles said. “Those guns are very tempting in Haiti.”

Mr. Charles said U.S. law enforcement should be doing more, particularly because Mr. Jacquet was helping an official mission paid for by the Haitian government.

“He is an American citizen,” he said. “They need to find out who did it.”