The Syrian Observatory for Human Rights says it was dropped by either Russian jets or the Syrian regime.
Do you remember how, once, the use of chemical warfare horrified us? It sat alongside genocide as the greatest of war crimes.
And yet the world remains unmoved by this. Why?
The atrocities of the World War II we said could never be repeated. And yet we're gassing people again.
There's a charity ambulance service operating in Idlib.
The man in charge of it is Mohammed Rasoul. He told the BBC his medics found people, many of them children, choking in the street and foaming from the mouth. Children. Toddlers.
And the Idlib medical centre posted a picture of at least seven dead children placed in the back of a pick-up truck - none of whom had any visible trauma to their bodies. Gassed to death.
The doctors on the ground say they're sure the chemical used is the nerve-agent sarin.
And it isn't the first time it's been used in Syria.
Remember in 2013? Those horrifying images that came in from Damascus when hundreds died in a sarin attack? 1500 were killed, including 400 children.
And what a failure that was on so many levels - not least from the US president at the time, Barack Obama.
The year before he'd given his famous red-line speech. He said "a red line for us is if we start seeing a whole bunch of chemical weapons moving around or being utilised".
And the following year the Syrian regime used sarin.
They've used chlorine as a weapon too. And Isis have used the blister agent "sulphur mustard".
But Obama did nothing. And now Syrian civilians have been gassed again.
France, among others, is calling for an emergency security council meeting, but what good will that do?
The Russians are part of the permanent five. They'll veto anything that's not in the Syrian regime's interests.
And so what do you do? You have to remove Assad from power. As long as he is there, this will go on.
He controls the chemical weapons. He's calling the shots. And hundreds of thousands have been killed by the regime. So how many more?
CNN is reporting a doctor saying "I've never seen anything like this - it's beyond description."
So what will it take? What will change without intervention?
Forget the UN security council. This needs one very powerful leader to step up. A leader to connect with the humanity of the situation, or perhaps the inhumanity, and stop history repeating itself.
And there's only one leader, isn't there? And his name is Donald Trump.
