American couple missing in Caribbean after fugitives allegedly steal their yacht: Police

An American couple has gone missing in the Caribbean after three escaped prisoners allegedly used their yacht to island hop before getting recaptured by authorities, according to investigators.

Ralph Hendry and his wife Kathy Brandel disappeared from their yacht, Simplicity, which was docked in the waters of the southern Caribbean nation of Grenada, Hendry's sister, Suellen Desmarais, told ABC News.

Police have not confirmed the identity and nationality of the couple but are investigating the incident.

Hendry and Brandel were last seen alive by their boating neighbor at the dock on Sunday afternoon, according to Desmarais. The neighbor said he saw the couple entering a restaurant, Desmarais said.

"That man went to bed that night and he looked over and Simplicity was there when he went to bed," but when the neighbor "got up at 6:30 a.m. on Monday morning, Simplicity was gone," she told ABC News.

Desmarais said the couple had been in Grenada for about two weeks, and their yacht left the island a week earlier than planned.

The Royal Grenada Police Force said the yacht allegedly became the target of three alleged criminals, Ron Mitchell, Trevon Robertson and Abita Stanislaus, all from St. Andrew, Grenada, who escaped from a police station after they were arrested on Sunday.

They were charged jointly with robbery with violence before their escape, police said. Mitchell was also charged with rape, attempted rape and indecent assault, according to investigators.

All three fugitives allegedly managed to make their way to a neighboring Caribbean country using the yacht, but they were caught by police in St. Vincent and the Grenadines on Wednesday, according to authorities.

Grenada Police said they are "currently working on leads that suggest that the two occupants of the yacht may have been killed in the process."

The Salty Dawg Sailing Association, a sailing association that the couple belonged to, said in a statement a good Samaritan boarded the yacht when anchored and abandoned off a St. Vincent beach and contacted both them and the Coast Guard when he found no one inside.

The good Samaritan allegedly "found evidence of apparent violence," according to the association.

"I have spoken to the families and have offered our deepest condolences and our assistance in any way possible. In all my years of cruising the Caribbean, I have never heard of anything like this," Bob Osborn, SDSA's president, said in a statement Friday evening.

The investigation is ongoing.

The couple, who lived on the boat, had been sailing the same route for a number of years, Desmarais said. That route started in Virginia, followed by a stop in Massachusetts, then to Florida to see Desmarais and her family, before heading south to island hop in the Caribbean.

Hendry and Brandel's two children and Desmarais' son traveled to St. Vincent and the Grenadines on Friday to join the search.

"Their love for life and island people, they're good, basic people," Desmarais said. "Until they find a body, they're still alive."