Events that occurred before the video began recording remain unclear but – later reported in court – the sinking of a wooden “pirate ship” by one of the other vessels in the video is said to have been what led up to the murderous actions captured on film.

There were at least four longliner ships on the scene, and the incident unfolded over more than 10 minutes in broad daylight. It is a chilling spectacle, particularly when, late in the footage, deckhands can be seen laughing and posing for photos amid the carnage.

There is no law requiring any of the witnesses to report the killings, and no one did.

Grainy video of this slaughter of at least four men in the Indian Ocean, somewhere between Somalia and the Seychelles in August 2012, has been circulating in the darker corners of the internet for years. Authorities only learned of the killings when the video turned up on a phone left in a taxi in Fiji, two years after the event.

Finally, on August 22 last year, Taiwanese authorities arrested a suspect: 43-year-old Chinese national Wang Fengyu, who they believe to be the man who shouted the orders to kill, from a ship registered in Taiwan. Investigators hope he will lead them to others.

On January 29 this year, Wang was convicted of homicide and violations of the Controlling Guns, Ammunition and Knives Act, the prosecutor’s office said.

An unknown number of similar killings take place each year – deckhands on the ship from which the video was shot told a private investigator, and later a documentary crew on camera, that they had witnessed a similar slaughter just a week earlier.

Trygg Mat Tracking, a Norwegian research firm that focuses on maritime crime, identified the ship as the Ping Shin 101, by comparing video footage with images held in a maritime database. Former deckhands on the vessel were identified through Facebook and other social media platforms where they had discussed their time on board.

Interviews with these deckhands, some of whom said they had witnessed the killings captured in the video, revealed the name of the captain and other details of the incident.

Officials from the Indian Ocean Tuna Commission, which licenses commercial fishing in the region where the killings occurred, and the Taiwanese flag registry – responsible for enforcing laws on Taiwanese-flagged ships – declined to provide information about the crew, the captains at the scene, the ships’ routes or their recent ports of call.

“It is nearly impossible to police the open ocean, and sometimes people take matters into their own hands, as was the case here,” says Klaus Luhta, vice-president of the International Organization of Masters, Mates and Pilots, a seafarers union. He notes that the murdered men appear to be unarmed and defenceless, and not to pose a threat.

“Whether this was some sort of vigilante justice or cold-blooded killing for reasons unknown,” he says, “we see clearly it is a vicious murder at sea.”

Such killings will continue to go unchecked, says Luhta, without better tracking of offshore violence, more transparency from flag registries and fishing companies, as well as more effort by governments to hold perpetrators accountable.

Prosecuting such crimes is essential, says US Naval Academy historian Claude Berube, because what occurs at sea affects everyone. By some estimates, 90 per cent of traded goods travel by sea, while seafood is a major source of protein for much of the world. Therefore if dumping oil intentionally, fishing in prohibited waters, enslaving deckhands or killing on camera go unpunished, says Berube, ship operators who are willing to break the law gain a competitive advantage.

Lawlessness at sea, he says, makes consumers complicit in human-rights and environmental abuses. “The public should be concerned with crimes at sea because those crimes don’t start or stop at sea,” says Berube. “They have land-based networks that affect lives and economies.”

But lawbreaking can be countered only when it is reported, which rarely happens offshore. Shipping and fishing companies, maritime insurers, private security firms, embassies and flag registries track violence at sea to varying degrees, but there is no single comprehensive centralised or public database.

The Stable Seas programme of the Colorado-based One Earth Future Foundation has been granted access to much of that information. Former US Navy officer Jon Huggins, a senior adviser to the programme, says the data includes a variety of crimes: robbers siphoning fuel, hijackings, human trafficking, piracy.

When programme officials tried to convince the groups that gathered the data to make it available to the public, Huggins says they pushed back. Risk management companies asked why they should share data they could sell instead. Coastal states worried it might scare away business. Flag registries were reluctant to release information that might oblige them to act, which they had little motivation or ability to do.

Complaints of crime at sea are rare. And, Berube says, many ships lack the insurance that would make reporting it worthwhile. Captains resist prying investigations that can cause delays. Most countries lack blue-water navies or coastguards that patrol beyond their territorial limits; they have neither the financial ability to patrol international waters of uncertain jurisdiction, nor any interest in doing so.

“We saw those challenges with Somali piracy a decade ago,” says Berube. “Merchant ships were largely told that they were on their own, and they took on private security teams in the absence of national or international support.”

But much has since been learned about the 2012 killings. Two Filipino deckhands on the Ping Shin 101, Aldrin and Maximo – both going by a single name only – told a private investigator on camera that they witnessed the murders.

In the video of the incident, Maximo is one of those who can be seen smiling and posing for selfies after the shooting. He wears an oversized blue T-shirt that reads “Hang 10”.

Aldrin and Maximo told private investigator Karsten Von Hoesslin in videotaped interviews that the Ping Shin 101 was about 370 miles (595km) southeast of the Somali capital of Mogadishu when it received a radio alert that a nearby ship had come under attack by pirates. It was unclear which ship was being attacked; there was shouting back and forth.

When the Ping Shin 101 arrived on the scene, joining fellow Kaohsiung-registered Chun I No 217 and two other fishing boats, it was fired on by a ship with four men on board, a court in Taiwan heard.

Deckhands aboard the Ping Shin 101 opened fire in retaliation, but the two witnesses claimed the supposed pirates in the smaller boat appeared to be unarmed. As they leapt into the water to escape the gunfire, they began shouting that they were not a threat. “No Somali!” one deckhand heard them say. “No pirates!”

Captain Wang claimed the firing was in self-defence, but the court ruled that he had ordered private maritime security guards from Pakistan on board the Ping Shin 101 to shoot and kill the four men he claimed were Somali pirates that day, even though they were no longer a threat.

A Vietnamese crewman who witnessed the shooting, who the prosecutors identified only by his surname, Tao, testified at the trial that the order given to shoot in the video sounded like Wang’s voice.

There is no indication that the two Pakistani guards who fired the weapons will be investigated or charged for their role in the murders.

According to ship-tracking records, the 165-foot Ping Shin 101 was owned by a Shanghai business executive named Lee Chao Ping, principal of Ping Shin Fishery, in Kaohsiung. Efforts to reach Lee were unsuccessful, and online records show that the business closed in 2018.

A security guard at its former address said in September that there was a Ping Shin or Ping Hsin fishery in the building some years ago but that the office had closed. Interpol and a private investigation firm specialising in maritime crime have also been unable to find Lee.

Duncan Kawino, who says he worked on the Ping Shin 101 when it docked in Mombasa, Kenya, in 2013, claims the vessel fished mostly in Somali waters, but reported that its catch came from the Seychelles territory, where he says it had a licence.

That August day a year earlier, the Ping Shin 101 and the nearby Chun I 628 each had three armed guards, all Pakistani, the witnesses said. The video shows at least four men being killed, but Aldrin and Maximo said it was likely that more were shot – as many as 10 to 15.

And then there was the matter of this not being an isolated incident. A similar confrontation occurred a week earlier, Aldrin said, and the circumstances he described on camera for a documentary series were virtually the same: suspected pirates were rammed, shot and killed, their bodies left floating in the water. A video that apparently captured the earlier attack was also discovered by Trygg Mat Tracking.

The Ping Shin 101 eventually ended up on the ocean floor. The vessel sank on July 7, 2014, less than two years after the shootings captured on the video. Wang, still the captain, broadcast a distress signal citing a mechanical failure. “Something exploded,” one crew member said on camera.

Prosecutors say they spent time trying to track down the vessel, but they were more interested in the man in charge. The captain never reported for questioning, so a warrant for his arrest was issued on December 28, 2018.

Wang is not alone in facing comeuppance for his actions on the often lawless high seas. In the past 12 months, Taiwan’s fishing fleet has been the subject of criticism from environmental, labour and human trafficking advocates as well as US government officials.

In March 2020, Greenpeace released a report that identified Taiwanese vessels and companies as some of the worst offenders when it came to labour and human trafficking violations among fisheries. They also found widespread illegal fishing practices including shark finning and illegal transshipments.

In September 2020, the US Department of Labor included fish caught from Taiwan in its list of Goods Produced by Child Labor or Forced Labor. In January 2021, Fong Chun Formosa Fishery, a Taiwan-based company linked to illegal fishing and labour violations, acquired Bumble Bee, a major supplier of tuna to US consumers.

Wang was arrested last year after the fishing ship in his charge, the Seychelles-flagged Indian Star, docked at Kaohsiung port, on the southwest coast of Taiwan. The vessel had a history of violations, including using forged licences and fishing in prohibited waters.

And so, eight years on from the month of the notorious video – one that if not for a phone being dropped in a taxi may never have come to light – a three-judge panel in Taiwan ruled that the killing of the unarmed men meant the captain was guilty of murder.

Now, caught on video, and with witnesses corroborating the murders, the next step in this precedent-setting case will see whether Wang exercises his right to appeal his homicide conviction.

“They didn’t have any guns, only fishing equipment on their boat,” said Maximo. “It was wrong, people getting shot, but there was nothing I could do about it.”