The volunteer lifts the corpse into a truck where a dozen already lie. As he does, the stretchers come one after another, each carrying another body retrieved from the river, most bearing gunshots to the head.
"We do not know who they are -- they were not carrying papers," he laments.
At the bank of the river in northern Syria, dozens of bodies in civilian clothes lie lifeless, covered in mud. Many of them bear wounds indicating gunshots at close range, and so are unrecognisable.
"We will take them to families to identify them," rebel captain Abu Sada offers. "Those who we cannot identify, we will bury in a common grave."
The bodies are among those of nearly 80 young men, all executed with a single gunshot to the head and neck, that were recovered on Tuesday from Quweiq River, which runs through Aleppo city.
A monitoring group said the death toll was at least 65, but added it could still rise significantly, and a rebel fighter put the figure at 78 dead, with more bodies still being retrieved from the water.
Near the river, hundreds of residents flock to the scene to see if they can spot a father, a brother, a son, or a husband.
"My brother disappeared weeks ago when he was crossing (through) the regime-held zone, and we don't know where he is or what has become of him," said Mohammed Abdel Aziz.
"It's possible he's here," he adds as he inspects a body covered in mud.
According to Abu Sada, around 30 bodies are still in the river, but cannot be recovered because of regime snipers positioned in a nearby neighbourhood.
"There must be over 100 -- many are still in the river, and we will try to retrieve them," he says.
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Abu Anas, another rebel fighter, notes this is not the first time he and his comrades have discovered multiple corpses at the same time, but adds, "never this many".
The bodies are taken to a school in the Yarmuk neighbourhood, and placed on the ground, covered with a blue cloth.
Each has a number beside it.
A nurse inspecting the bodies says, "There are those who drowned because the were shot in the legs or abdomen before being thrown into the water," and notes that some of the victims may have been killed as far back as three days ago.
In the school yard, the smell is nauseating, and families pass in front of the bodies, covering their faces with tissues or their clothes.
Only the faces of the victims are visible to passers-by, so they can be identified and buried.
"These are civilians -- there is a child among them who was also executed in cold blood," says Abu Saij, a rebel fighter. "Ordinarily, we would retrieve two or three bodies in a day -- never before have we seen such a thing."
"Yesterday, they (pro-regime forces) were unable to take control of Bustan al-Qasr (a neighbourhood in southwest Aleppo), and so they took revenge," Abu Saij continues.
"Some of these corpses date back several days, but most were executed recently."
A senior government security source said many of the victims were from Bustan al-Qasr and had been reported kidnapped earlier.
He accused "terrorists," the standard regime term for people fighting to overthrow President Bashar al-Assad, of the killings and spreading propaganda to deflect responsibility.
But Abu Saij insists rebels are not to blame.
"The regime threw them into the river so that they would arrive in an area under our control, so the people would think we killed them," he says.