SEOUL, South Korea >> In early November, two North Korean fishermen captured in South Korean waters were escorted to the inter-Korean border, blindfolded and their bodies tied with ropes​. There, they were handed over to North Korean authorities.

South Korea often reveals the seizure of North Korean fishermen in its waters once it happens. This time, the episode was kept secret — until an army ​officer on the border sent a text message ​reporting the handover ​to a senior presidential aide and a photographer captured the message on the aide’s smartphone​.

​R​evelation after shocking revelation​ has since followed, leaving human rights advocates and groups that include South Korea’s bar association agape with outrage.

As legislators looked into the matter, officials admitted that the two ​fishermen, ages 22 and 23, submitted ​hand-​written statements ​in which they said they hoped to defect to South Korea. ​But after a few days of interrogation, South Korea concluded that they were not refugees needing protection but “heinous criminals” who butchered the captain and 15 other crewmen on their boat.

The two were denied access to lawyers, a court hearing or a chance to appeal the government’s decision to repatriate them.​ Until their blindfolds were taken off at the border, they did not know where they were being taken. When they finally realized it, one of them collapsed, according to lawmakers briefed by officials.

For the two men, their return to North Korea could mean their likely execution.​

Tens of thousands of North Koreans have defected to South Korea since the end of the 1950-53 Korean War. ​Until now, the South had accepted all defectors, regardless of their criminal records, because North Koreans technically qualified as South Korean citizens under the South’s Constitution.

For years, the United Nations​ ​has ​lamented widespread lack of due process in North Korea​, reporting torture, starvation, murder and other crimes against humanity perpetrated against criminal suspects, especially those forcibly repatriated from abroad. ​

“Forcibly repatriating ​them was an act against​ ​humanity that violated international law,” Won Yoo-Chul, an opposition lawmaker, told ​a highly emotional parliamentary hearing last month. “Their repatriation constitutes a murder through willful negligence because South Korea sent them to the North, fully aware that they would be executed there.”

The case of the two fishermen was also unusual because it marked the first in which South Korea rejected North Korean defectors because of their alleged crimes in the North or because their intent to defect was considered disingenuous.

In a joint statement this week, Human Rights Watch and 66 other rights groups ​accused ​​South Korea ​of failing in its obligation under international treaties to “protect anyone who would be at substantial risk of torture or other serious human rights violations after repatriation.”

​Few personal details have been revealed about the two North Korean​s, except that one was the boatswain and the other a deck hand. But their fateful journey began Aug. 15, when their 17-ton wooden boat with 19 men on board cast off from Kimchaek​ on the east coast of North Korea, South Korean​ officials said.

The two​, together with the ship’s chief engineer, mutinied against the captain’s abuse ​on a late October​ night​, killing him with hammers and axes. They then went on a killing spree to hide their crime. They awakened the​ir ​colleagues two at a time, lured them outside and butchered them, throwing their bodies overboard.

They steered their ship back to Kimchaek, hoping to sell the squid and flee inland​. When the engineer was arrested by Kimchaek​ police​, the other two fled back to the sea.

By the time their boat ​approached the inter-Korean sea border on Oct. 31, South Korean authorities said they had picked up intelligence that ​North Korea was looking for ​them. South Korean patrol boats fired​ warning shots and broadcast warnings, a standard procedure when a North Korean fishing boat crosses the border without signaling that those on the boat are defecting​.

The boat repeatedly crossed back and forth across the maritime border for two days, until South Korean navy commandos ​finally ​seized ​it on Nov. 2.​ Both men quickly confessed to mass murder, providing identical details of the​ crime during separate interrogations, South Korean officials said. They then said they wanted to defect to the South​.

“We decided to expel them because they were atrocious criminals who could threaten the lives and safety of our people if accepted into our society,” said the South Korean unification minister, Kim Yeon-chul,​ who added that the two “lacked sincerity when they said they wanted to defect.”

Few matters ​are that simple on the divided Korean Peninsula, however.

Although the South’s Constitution claims North Korea as part of its territory, both ​sides in reality have also recognize​d​ each other’s territorial sovereignty. They joined the United Nations at the same time, and have held summit meetings and signed agreements to bolster economic and other forms of cooperation. In the past decade, South Korea has returned 185 North Korean fishermen adrift in its waters​ who wanted to return home. In the same period, North Korea sent home 16 South Koreans who entered the North illegally.

In previously holding to its policy of never returning any North Koreans who said they wanted to defect, the South had welcomed people with tainted pasts. At least 270 ​North Korean defectors living in the South were found to have ​committed crimes serious enough to disqualify them from government subsidies, including nine who had committed murder or​ other serious ​offenses, according to government data.

“I am just flabbergasted,” wrote Joo Sung-ha, a defector-turned-journalist in Seoul​, referring to the South’s refusal to believe the two North Koreans’ stated intention to defect. “If they defected​ to the South, they ​had a chance to live, and if they ​returned to the North, ​it was 100% ​certain that they ​would die. Under such circumstances, ​wasn’t it natural for them to want to defect?”

Rights advocates were especially disappointed because the office of President Moon Jae-in coordinated the repatriation. Before winning the presidency, Moon ​had been a famed human rights lawyer who once defended six Korean-Chinese men who ​murdered 11 ​crewmen, including seven South Koreans, on a tuna fishing boat in 1996.

“President Moon Jae-in and his government are ignoring North Korea’s grave human rights abuses in a misguided effort to mollify Kim Jong Un and improve relations with Pyongyang,” said Phil Robertson, the Asia deputy director at Human Rights Watch.

​Instead of hurrying to repatriate the​ two North Koreans, South Korea should have thoroughly investigated the case​, including “whether ‘the brutal criminals’ were in reality not the abusers but victims of the harsh circumstance of North Korea,” Ra Jong-yil, the former deputy director of the South’s National Intelligence Service, wrote in the JoongAng Ilbo newspaper.

But under ​its legal system, South Korea could not have prosecuted the two men because the criminal evidence was in the North​, officials and other lawmakers said​. They feared that letting the two North Korean fishermen stay free in the South would have been a betrayal of the victims of their alleged crime, and might help turn South Korea into a safe haven for criminals on the run from the North.

“This is one of the best things the Unification Ministry and the National Intelligence Service have done recently,” said Lee Seok-Hyun, a governing party lawmaker, referring to ​the agencies involved in the repatriation.​

Conspicuously absent from the debate​, however​, are the voices of the two North ​Koreans who were sent back to their homeland. Since they were returned, North Korea has not spoken a word about their fate.