moved a heavy arsenal of weapons into place. weapons leading to the shoot down, according to u.s. intelligence. there was a convoy about several weeks ago, about 150 vehicles with armed personnel carrier, multiple rocket launchesers, tanks, artillery, all crossing over from russia, into the eastern part of ukraine and was turned over to the separatists. reporter: within minutes of flight 17 dropping off radar, the u.s. suspected shoot down. experts narrowing in on two-piece of critical intelligence. first a surface-to-air missile system had been activated in a separatist controlled area in eastern ukraine. a moment later, a u.s. satellite captured the heat signature of a midair explosion. we detected a launch from that area and our trajectory shows it went to the aircraft.