Three days ago, an extended video popped up on Youtube of five mariners being shot to death in the open ocean on the wreckage of their boat, as their killers guffaw and chatter from the decks of their larger crafts. Where was the footage shot? Who were the victims and their killers? So far, no one knows for certain.

The very graphic footage above, which appears to have been recorded by a member in the killing party, shows the victims clinging to the underside of a tiny boat as small arms fire erupts around them. One by one, the men are picked off, left to float in billowing clouds of blood as their killers laugh and pace the weatherdeck of their ship. It's a grisly mystery that's now under investigation by Interpol and representatives of multiple governments.

The video, which was reportedly found on a cell phone left in a cab by a Fijian fisherman, was uploaded to Youtube August 17 under the title "Fishing vessel fijian crew gettin shot, out side fiji waters," but Agence-France Press reports that government officials dispute that description:

Fiji naval commander John Fox said inquiries had confirmed the victims were not from the South Pacific nation, where no fishermen have been reported missing recently.

"We are aware of the video and we conducted our investigations," Fox told the Fiji Times.

"I can't say how we were able to verify the information but I can confirm that they are not Fiji citizens."

Reporters and interpreters from Television New Zealand identified one of the killers' three ships, which can be clearly seen at one point in the video, as Taiwanese and suggested that the victims may have actually been criminals themselves:

Fiji Tuna Boat Owners' Association president Graham Southwick told the broadcaster that indications were that the shooting victims were Somali pirates involved in a failed hijacking.

"We checked with all our Taiwanese boats and various things and they said 'oh yeah we know about this story, it happened about a year or 18 months ago and the guys in the water being shot are Somali pirates'," he told TVNZ.

But Voice of America suggested the victims were actually "fishermen from an unflagged small boat":

Specialists in several countries, who have examined the video, speculate the distressed men in the water, who presumably were all killed, were likely from the east African coast or the Arabian Gulf area.

A few critical details are known: The largest of the killers' ships circling the victims is "the Seychelles-flagged Taiwan-owned Chun 1 No. 217," according to VOA, "a 725-ton fishing boat with a home port of Kaohsiung and managed by the Tching Ye Fishery in the same city." And on the videographer's boat, where much of the shooting comes from, "Mandarin, Cantonese, Vietnamese, Thai and other languages" can be heard on deck and over the intercom.

At the video's conclusion, the cameraman pans across the bow of his ship, showing the faces and casual clothing of the triumphant murderers as they celebrate and snap selfies on cell phones.

Regardless of whether or not their victims were violent pirates, the shooters are clearly guilty of "an entirely unlawful summary execution of five men," a maritime expert and Royal Marines veteran told VOA, adding: "The context and the time, as in when the footage was taken, actually is secondary to the issue that there have been criminal acts of homicide that have taken place from a registered commercial fishing vessel in international waters."