It is the smell that forewarns you of the horrors to come.
The nauseating stench of death reached out from the warehouse, curling around us, like a physical presence.
Inside the warehouse, under a still smouldering roof - we saw the charred remains of more than 50 bodies. Some were little more than skeletons. They were killed on Tuesday, in the dying days of the regime.
There were more bodies on the ground outside. A rope was still attached to one man's feet. We can't be sure how many more were killed in the compound. Local people had removed some bodies for burial on Saturday.
A gaunt elderly man, Fathallah Abdullah, wept in the warehouse doorway. He told us that he managed to escape the massacre inside, but without his three sons - Ibrahim, Abdul Hakim, and Ali. All four had been detained in mid-August in their hometown of Zlitan.
"I was there," he said pointing to a corner littered with skulls. "My sons were beside me. The whole area was packed with people, crowded in like animals. We were on top of one another. There was no space to put your feet down on the floor."
Up to 150 civilians from different parts of Libya were being held there, according to Fathallah. He says uniformed troops and mercenaries guarded them. Another survivor gave a similar estimate of the numbers.
The prisoners had been asking for water. The guards promised to bring it at sunset, but instead they came with guns.
"They started shooting," Fathallah said. "Then they threw grenades, three of them. They stopped and came back and started again."
When another prisoner kicked open the warehouse door Fathallah ran for cover and managed to hide under a truck. He says he lay there for hours, listening to a massacre he was powerless to stop.
"They were shooting up until two o'clock or three o'clock in the morning," he said. "Whoever is still alive they kill him."
Fathallah is certain that two of his sons were killed in the warehouse.
He is clinging to the hope that the third, Ali, may have survived, but there seems little chance of that. There has been no sign of him since the shooting stopped.
"My sons were just ordinary men but they were well liked by everyone," he said, his face wet with tears.
Outside the warehouse he greeted another survivor, Ali Hamouda, with a sombre handshake. Ali was uninjured but told us his cousin was among the dead.
Both men said some of Col Gadaffi's own troops were not spared. They too were imprisoned in the warehouse, presumably for not following orders.
"The soldiers were in the middle," Ali said. "They were sitting on blankets. They took them outside first. After that we heard gunshots. Maybe they executed them. Then they start to shoot us."
Visitors trickled into the compound on Sunday morning. There were shaken local residents and armed and angry rebels.
Some covered their mouths and noses trying to keep out the stench. One young man collapsed in grief and had to be helped away.
We know now that this warehouse compound was the location where a BBC team was held in March.
During their detention they were beaten and subjected to mock executions. One member of the team, BBC technician Chris Cobb Smith, returned to the scene on Sunday.
He identified the cell alongside the warehouse where the team had been held, and terrorised.
"We spent most of the night in that cell," he said.
"I must have watched every second tick by. We definitely heard people being beaten, and moved around in the compound. I think if it had been later on in the conflict, things may have turned out very differently for us."
Local people say the area around the Khamis Brigade Headquarters is a killing ground. We were told that human remains had already been recovered in several locations and removed for burial.
When we visited one site, behind a mosque, we saw fresh burn marks on the ground where bodies might have been torched
As residents begin to reclaim their neighbourhoods, and the opposition take control of more of the regime's compounds, the fear is that more atrocities will come to light.
Libya's National Transitional Council (NTC) estimates that between 57,000 and 60,000 men were arrested by Col Gadaffi's regime in the past six months. Around 10,000 have been freed.
The rebels are now asking, with increasing concern, where are the others?
As we left the warehouse local residents and survivors of the massacre were compiling lists of the dead, and recording information about those accused of killing them.
They may be hoping for justice in the new free Libya those in the warehouse did not live to see.