A Chinese boat captain, who is suspected of ordering the killing of at least four unarmed men at sea some six years ago, was detained by Taiwanese authorities on Saturday soon after he entered Kaohsiung port on a fishing boat.

The 43-year-old suspect was arrested when the Seychelles-flagged Indian Star docked in the southern port city at 8:50 a.m. Saturday, the Coast Guard Administration's investigation unit in Fengshan District said, CNA reports

According to Taiwan media reports, the suspect is a Chinese citizen, Wang Fengyu, but while local authorities confirmed his nationality, they did not release his name.

The man is suspected of involvement in the deaths of at least four unarmed men, who were shot as they were drifting in the water, clinging to some debris. It was not clear why the victims were in the water.

The case came to light after a 10-minute video was circulated on the internet in August 2014, in which a man believed to be a boat captain could be heard giving directions to the crew, while 40 rounds of live ammunition were being fired, picking off the unarmed men in the water one by one.

In the video, the voice of the captain can be heard directing the shooting, speaking in Mandarin with a mainland China accent, while the crew members chatter in Vietnamese.

"In front, to the left! What are you doing? In the front, to the left!" the man screams in the recording. "Open fire, open fire, open fire!"

Finally, all of the victims are seen floating face down, their blood staining the blue water around them, and the group of men filming the killings from the deck of the boat pose for photos as their vessel continues on its course.

No footage of the shooters is shown in the video, but a Taiwanese fishing vessel with the identification number BI-2353 is seen passing in the background just before the shooting started.

The 725-ton longliner is registered to Tching Ye Fishery Co in Kaohsiung, and the owner of the vessel, surnamed Lin, told international media at the time that he did not know if his ships were at the scene when the men were shot.

Lin also declined to reveal details about his vessel's crew but said there were private security guards on his ship, who were provided by a Sri Lankan company that he declined to name, according to international media.

The video was believed to have been uploaded on the internet after it was discovered on a cellphone that was found in the back of a taxi in the South Pacific country of Fiji, international media reported.

International maritime safety groups and other experts analyzing the video suspected that the two ships -- the one from which the shots were fired and the one seen passing by -- may have both belonged to the same owner, whose boats normally operate in pairs in the Indian Ocean.

But efforts to get more information from the owner of the Taiwanese boat in the background and Taiwan's Fisheries Agency, which would have data on the crew and locations of Taiwan-registered ships, have been fruitless.

On Sunday, the Kaohsiung District Prosecutor's Office declined to say whether the suspect who was arrested had been working on a Taiwanese vessel at the time of the shooting or to identify the boat.

It is not uncommon for Taiwanese ship owners to hire mainland Chinese captains to supervise mostly Southeast Asian crews.

A few years ago, Taiwan's government began allowing the country's vessels to hire armed security guards to deal with a spate of piracy -- robberies at sea -- and hostage taking for ransom.

It is not clear whether the government regulations allow the shooting of unarmed pirates, particularly if they are in a dire situation like the men in the video, who were trying to stay afloat.

Taiwan's prosecutors on Sunday also declined to say whether the suspect had entered Kaohsiung port on a Taiwanese owned vessel.

After the video was uploaded on the internet, there was initial speculation that the victims were Fijians, but an investigation by Fijian police found that they were not, Fiji media reported.

At that time, Fiji Police Commissioner Major General Ben Groenewald said their investigations showed that the video was shot outside of Fiji waters and involved a confrontation between an Asian fishing crew and pirates somewhere in the Indian Ocean, according to a Fijian Broadcasting Corp. report on Aug. 26, 2014.

Investigations further established that the video was first viewed in mid-2013, the report said.

"Fiji police say the case is now closed, and they will not be making any further comments on the matter," the Fijian Broadcasting Corp. said in the report.

However, the inter-governmental organization International Criminal Police Organization (INTERPOL), suspecting that a Taiwanese person may have been involved, had handed the case to Taiwan criminal investigation units for investigation.

On Saturday, the Kaohsiung District Court ordered the detention of Wang, citing his suspected involvement in major offenses and the likelihood that he would attempt to flee the country.

The court also ruled that he be held in isolation, in keeping with Taiwan's virus prevention measures. Prosecutors, meanwhile, said their investigation is ongoing, and they declined to give any further information.

A fishing port in Kaohsiung in Taiwan.

Chinese skipper arrested in Taiwan for shooting murder of four adrift at sea