certainly not by the syrian government or by russia. they say what happened is the assad regime attacked, quote, a terrorist weapons depot in this area, and because of that explosion, toxins were released that were being stored there, causing these casualties. however, a u.s. intelligence official has told nbc news it appears to be -- may have been a deliberate chemical weapons attack. >> reporter: the images are horrific and hard to watch. they show the telltale signs of a chemical weapons attack. no blood, only the dead and injured on the ground after quickly sum co quickly k quickly suck coming to poisoned gas. this boy using all his strength to breathe. the victims' clothed ripped off to wash off the toxin. >> the gas attacks are