Speaking for the administration the second time this week, Secretary of State John Kerry laid out some of the unclassified evidence pointing to Bashar al-Assad’s responsibility for the chemical weapons attack and brushed off the need to have the United Nations on board to take action against the regime.

Kerry said the U.S. government has ascertained that at least 1,429 Syrians were killed in this attack, including at least 426 children.

The findings of the intelligence committee, he stressed, “are as clear as they are compelling.”

“I’m not asking you to take my word for it. Read for yourself, everyone, those listening, all of you, read for yourselves the evidence from thousands of sources, evidence that is already publicly available,” he said. “And read for yourselves the verdict, reached by our intelligence community about the chemical weapons attack the Assad regime inflicted on the opposition and on opposition controlled or contested neighborhoods in the Damascus suburbs on the early morning of August 21st.”

“Our intelligence community has carefully reviewed and re-reviewed information regarding this attack. And I will tell you it has done so more than mindful of the Iraq experience. We will not repeat that moment. Accordingly, we have taken unprecedented steps to declassify and make facts available to people who can judge for themselves.”

What’s not available for public consumption is evidence that could betray “sources and methods,” which will only be available to members of Congress.

Kerry then dove into the unclassified facts.

“We know that the Assad regime has the largest chemical weapons programs in the entire Middle East. We know that the regime has used those weapons multiple times this year, and has used them on a smaller scale but still it has used them against its own people, including not very far from where last Wednesday’s attack happened,” he said. “We know that the regime was specifically determined to rid the Damascus suburbs of the opposition, and it was frustrated that it hadn’t succeeded in doing so.”

“We know that for three days before the attack, the Syrian regime’s chemical weapons personnel were on the ground in the area, making preparations. And we know that the Syrian regime elements were told to prepare for the attack by putting on gas masks and taking precautions associated with chemical weapons. We know that these were specific instructions,” Kerry continued.

“We know where the rockets were launched from, and at what time. We know where they landed, and when. We know rockets came only from regime-controlled areas and went only to opposition-controlled or contested neighborhoods. And we know, as does the world, that just 90 minutes later all hell broke loose in the social media.”

The intelligence community included  video from the attack aftermath in its determination. One activist who runs the Violations Documentation Center in Syria told Foreign Policy magazine that of their citizen journalist crew who sped to the area to document the horrors, all but one died from exposure to the nerve agents.

“With our own eyes we have seen the thousands of reports from 11 separate sites in the Damascus suburbs. All of them show and report victims with breathing difficulties, people twitching with spasms, coughing, rapid heartbeats, foaming at the mouth, unconsciousness, and death. And we know it was ordinary Syrian citizens who reported all of these horrors,” Kerry said.

“And just as important, we know what the doctors and the nurses who treated them didn’t report — not a scratch, not a shrapnel wound, not a cut, not a gunshot sound. We saw rows of dead lined up in burial shrouds, the white linen unstained by a single drop of blood.”

He confirmed that many first responders were also affected, and “became victims themselves.”

“This is the indiscriminate, inconceivable horror of chemical weapons. This is what Assad did to his own people,” the secretary added.