Yesterday's incidents appear very different. Even on the lowest estimate of 400 to 500 dead, they would amount to the worst use of nerve gas since Saddam Hussein killed 5000 Kurds in the town of Halabja 25 years ago.
One video shows a room filled with the bodies of children. One or two small corpses are covered with sheets, others face the ceiling with closed eyes, wearing blue, orange and red T-shirts. Their feet are bare, for they were clearly asleep when overwhelmed by whatever killed them. If they had the chance to wake, it was not for long.
In the video's next image, there are 30 or so bodies. They lie in three ranks, some with arms neatly folded in front of their chests. In another video, the bodies of children have been covered with a black sheet held down by blocks of ice.
The attack appears to have taken place after rebels in eastern Damascus repelled several days of assaults mounted by Assad's forces. Most of these suburbs have been out of government control for over a year, but Ghouta, where the deadliest chemical weapon assaults are alleged to have happened, lies on a key supply route.
Consequently, the regime has made repeated and determined efforts to retake this area.
One doctor, who did not give his name, said that between four and six missiles loaded with chemical warheads struck the suburb of Zamalka at about 2am local time. "Are these the terrorists they are talking about, these children?" he asked.
"In one hospital, there are 155 people dead. Look at these women and children, entire families: 12 people in one family - the mother, the father, the children, and the grandfather. We found three buildings, all their inhabitants dead."
Mohammed Al-Said, an activist who shot one of the videos, said he found a building full of dead and wounded people. Some were shaking violently.
"The chances of rescuing the children were limited. They were arriving dead at the medical centre. About 10 missiles were fired. All the inhabitants within a circle of 200 metres of where they dropped were killed."
There are adult victims in the footage as well. One or two wear military fatigues, suggesting they were rebel fighters, but most do not and many are women.
The common feature of all the footage is the lack of blood. No bullet wounds are visible; there are no smashed faces, shattered limbs, or injuries inflicted by bombs, guns and knives.
The condition of the victims provides the clearest evidence that chemical weapons were used.
"It does seem that some kind of attack did occur and it does seem to have been a poison gas attack in some form," said Dina Esfandiary, an expert on weapons of mass destruction at the International Institute for Strategic Studies.
She pointed out one oddity. Assad's regime has three kinds of nerve gas: sarin, mustard gas and VX. The symptoms they inflict are, respectively, convulsions, skin blistering and immediate death. Many of the living victims in the footage display neither of the first two signs.
Esfandiary said there could be a simple explanation: the regime might have used a mixture of sarin and mustard gas for this particular attack.
The Syrian National Coalition, the main opposition group, claimed that perhaps 1300 people were killed. The Damascus Media Office, an opposition monitoring centre, said incidents had taken place in six suburbs of the capital and the death toll stood at 494, although it was unclear whether chemical weapons were involved in every case.
Rami Abdul-Rahman, of the London-based Syrian Observatory for Human Rights, said "poisonous gas" was fired from rockets, inflicting at least 100 deaths. The regime's official news agency, Sana, denied any chemical weapons had been used, calling the reports "baseless".
Whatever the final toll, any gas attacks would have an effect out of all proportion to the number of people they kill.
"They fulfil their purpose by scaring everyone," said Esfandiary. "We all know that chemical weapons are effective weapons of terror."
