Erez, 38, from Tel Aviv, claims he encountered a pirate ship two days ago, and was forced at gunpoint by the crew to allow the wanted man to board. Only later did he learn the man was wanted by Colombian authorities.
Erez and his wanted passenger are being led by the Colombian Navy away from international waters and towards Colombia, and Erez fears he could face arrest upon his arrival there.
Erez left Israel on his sail boat last month, and recently arrived in Panama, according to his sister, Karin Erez Azulay.
In Panama, the local Chabad House introduced him to an Israeli couple for a three-day sail. After dropping them off on Monday, Erez left for Jamaica.
"When he was in international waters, a group of fishermen/pirates stopped him and forced him—by threatening him with a loaded rifle—to take a man he did not know to Jamaica on his boat. He was forced to oblige them out of fear for his life," Karin wrote in a Facebook post that has gone viral.
"Several hours ago, a Colombian missile ship with soldiers violently took over his boat, causing great damage. At present, they are towing the boat to Colombia, with five armed soldiers on board as well as my brother Roy Erez and the wanted passenger," she added.
She went on to say that her brother "is concerned by the aggression used against him and of what might happen to him once he gets to Colombia. He's in this situation against his will and feels helpless. He's very concerned he'd be tied to a matter he has no part in."
The yacht is being towed toward the San Andrés Navy base in Colombia.
"We're very worried and want to bring Roy back home safely," the sister concluded.
Erez is an aquafarmer and was on his way to Vanuatu, a South Pacific Ocean nation made up of roughly 80 islands, to open up a fish farm, his friend Liran Golob said.
"He was stopped 240 miles from San Andrés. It was in international waters and they were not allowed to take over the boat," Golob said. "Roy is sailing under a German flag. He was sailing on his own."
"He's a very good guy who helps people. Sometimes he's very innocent. He said a fishing boat came near him and at gunpoint made him take in a man who later turned out to be wanted. (Roy) didn't know what (the man) was wanted for," Golob added.
Since Erez is a dual Israeli-German national, the family turned to both Israeli Foreign Ministry and to the German Embassy for help.
The Foreign Ministry said Israel's consul general in Bogotá, Yuval Sharabi, is looking into the details of the incident with the help of local contacts.