American husband and wife missing in Caribbean are likely dead, authorities say

An American husband and wife who went missing after three escaped prisoners boarded their boat in the Caribbean are likely dead, authorities said on Monday.

Ralph Hendry and his wife, Kathy Brandel, from Falls Church, Virginia, disappeared last week from their yacht, which was docked in the waters off the southern Caribbean nation of Grenada, according to Hendry's sister, Suellen Desmarais.

"It's a phone call you hope you never get -- shock, fear, anger," Ralph Hendry's son, Bryan Hendry, told ABC News.

Hendry and Brandel were last seen alive by their boating neighbor at the dock on Feb. 18, according to Desmarais.

The next morning, the neighbor said the couple and their yacht, Simplicity, were gone.

The three escaped prisoners allegedly stole the boat before heading to the nearby island of St. Vincent, where they arrived on the yacht on Feb. 19, police said.

"While sailing from Grenada, the suspects committed several criminal acts, including bodily harm, to the couple," Junior Simmons, head of the public relations and complaints department at Royal St. Vincent and the Grenadines Police Force, said in a video statement Monday.

"Based on the investigation thus far it is presumed that Ralph Hendry and Kathy Brandel are deceased," Simmons said.

St. Vincent police processed the scene on the yacht and found signs of violence, Simmons said.

"Several items were strewn on the deck," Simmons said, and in the cabin was "a red substance that resembled blood."

The three suspects were arrested on Feb. 21 and are cooperating with investigators, police said. They appeared in a St. Vincent court on immigration-related charges and pleaded guilty, police said. Sentencing was scheduled for March 4, police said.

Ralph Hendry and Kathy Brandel have been married for 27 years. They've been living on their boat since they sold their home in 2013.

"They were very risk-averse people, so they were extremely meticulous in their preparations and not willing to take this trip until they were 100% confident in themselves," Bryan Hendry said.