A graphic video in which castaway fishermen are murdered on the high seas is yielding information on the killers, a London-based human rights group says.
"I have shot five bodies," a man who had been shooting at the men in the water says.
The London group Human Rights at Sea (HRAS) said it was investigating the murders of the five seafarers first revealed when a video on the killings was posted onto YouTube from Fiji. The Pacific Island nation hosts dozens of Asian deepwater fishing boats.
It was initially believed the dead men were Fijian but it is now unclear where they were from.
All that has been established is that a vessel seen near the killings, Taiwan flagged Chun I No 217, was until last year licensed to fish in the Indian Ocean and the Tasman Sea.
Its location for the last three months remains unknown.
HRAS said it had analysed the 10 minute 26-second mobile-phone video and with language experts had established that Mandarin, Cantonese and Vietnamese was being spoken on the ship as the men were killed.
HRAS said: "The people involved represent a mixed crew on board what appears from all the evidence available to date, to be Taiwanese-registered fishing vessels."
The translations begin at the 2min 20sec mark when somebody says, "watch ahead, ahead, there are one or two people!"
At 2:34 somebody in a very low voice says: "We fire or not?"
Somebody trying to speak Chinese says: "Shall not we shoot?"
At 2:49 somebody says: "Impossible!"
At 3:10: "Swim faster!"
The first shots are fired at 3:17 and the first man is dead by 3:26.
Nearly three minutes later at 5:55 somebody says, "Make it end faster!"
The gunman appeared to have trouble killing a man clinging to wreckage.
At 6:45 someone says: "Finish it!"
Another man was swimming near the wreckage.
The translation shows that they were looking for others in the water until 8:02.
"He is coming over."
At 8:32: "To the front! Prepare go to front! What are you doing? To the front."
At 9.02: "Fire, fire, fire."
At 9.15 a man, speaking in Cantonese, says "OK" and then "the objects have been shot."
The translation ends at 9:30: "I have shot five bodies."
HRAS said the translation appeared to indicate that either the master/captain, or someone with authority was "directing and ordering the individual committing the acts of murder to shoot into the sea at the unarmed seafarers".
Some kind of command relationship was taking place, "between the individual giving the commands, direction and guidance, and the individual firing the shots", it said.
"[There] appears to be voiced uncertainty by that individual and/or others around, as to whether or not shots should be fired prior to the direct order to fire."
HRAS said it was in no doubt now that one man murdered all five victims.
"If the person ordering the firing of the deadly shots is the master/captain, or a senior crew member onboard, then there appears to be a joint enterprise to commit a criminal act, at the very least as between those persons," HRAS said.
It remains unknown who carried out the act.
Official data has identified a tuna boat seen nearby as the men were killed in the water.
But the Taiwan flagged Chun I No 217 has not switched on its vessel monitoring system device for three months and its whereabouts were unknown, monitoring sources told Fairfax Media.
High seas fishing boats are legally allowed to turn off VMS to keep a competitive advantage.
Up until last year Chun I No 217 was registered to catch southern blue fin tuna in waters around New Zealand and south of Australia.
Its registered owners in Kaohsiung City in Taiwan have not answered supplied telephone numbers on various registration documents linked to the vessel in the Pacific, Tasman and Indian Ocean regions.
There is no evidence the 725-ton Chun I No 217 was involved in the incident. It was identified only by one of its registration numbers, issued by the Seychelles, along its hull as it steered away from the ship where the shooting was occurring.