Things to note is when the first train (grain) goes into emergency braking involuntarily — that's because the train air line broke when it derailed, triggering an emergency braking. This is different from the oil train voluntarily going into emergency because its engineer "big holed" it (hit the emergency brake). By the time the oil train went into emergency, it was too late, though.
This video mostly has no sound until near the very end, when you hear the radio call of a railroad signal maintainer (truck visible earlier in the video) calling that he'd seen something go wrong, and of the crew of the oil train calling after they'd derailed and crashed off the rails telling the dispatcher they were on fire and that they were getting out of their train immediately.
Personally, I'm amazed the crew of the oil train stuck around as long as they did, and that they escaped relatively uninjured from what could have been a deadly pile-up.