What caused the accident? A step-by-step sequence of a chain of failures that the system did not stop We reproduce the sequence minute by minute using position data from Ranfa, official documents, the three audios from the Atocha control center that came up, explanations from the Minister of Transportation, conversations with train drivers, published information and the first comment of fence researchers. It is a temporal chronology, distinguishing what is proven from what is hypothesized and pointing out the fallacies that are revealed.