The official said a drone operated by Russians was flying over a hospital as victims of the attack were rushing to get treatment. Hours after the drone left, a Russian-made fighter jet bombed the hospital in what American officials believe was an attempt to cover up the usage of chemical weapons.
The senior official said the U.S. has no proof of Russian involvement in the actual chemical attack in northern Syria.
But the official said the presence of the surveillance drone over the hospital couldn't have been a coincidence, and that Russia must have known the chemical weapons attack was coming and that victims were seeking treatment.
Although Russia has steadfastly supported Syrian President Bashar Assad's government, and they've coordinated military attacks together, Washington has never previously accused Moscow of complicity in any attack that involved the gassing of innocent civilians, including children. The former Cold War foes even worked together in 2013 to remove and destroy more than 1,300 tons of Syrian chemical weapons and agents.
Until Monday, U.S. officials had said they weren't sure whether Russia or Syria operated the drone. The official said the U.S. is now convinced Russia controlled the drone. The official said it still isn't clear who was flying the jet that bombed the hospital, because the Syrians also fly Russian-made aircraft.
U.S. officials previously have said Russians routinely work with Syrians at the Shayrat air base where the attack is supposed to have originated. U.S. officials say the chemical weapons were stored there and that those elements add to the conclusion that Russia was complicit in the attack.
Earlier it was reported that Britain’s Defense Ministry said Russia was responsible for every civilian death in chemical attack in Syria. Moscow bears responsibility as the "main sponsor" of Assad’s regime.