Kerry says Syrian regime personnel were at the site of the attack for three days beforehand, making preparations.
He says regime elements were told to prepare by putting on gas masks.
Kerry says the U.S. also knows where the rockets were launched from. He says the rockets came from regime-controlled areas.
Kerry also says a senior regime official confirmed that the weapons were used and was afraid it would be discovered.
The U.S. is releasing a public report on intelligence gathered about last week's deadly attack. President Barack Obama is preparing for a possible military strike in response.
Take ABC13 with you!
Download our free apps for iPhone, iPad, and Android devices