She entered the subway without a headscarf. What happened next?

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At 6:52 a.m., she took the escalator into a metro station in the Iranian capital of Tehran, her short, dark hair uncovered. Roughly 16 minutes later, the girl — identified by authorities and activists as 16-year-old Armita Geravand — was lying, seemingly unconscious, on the subway platform.

These details were gleaned from a patchwork of security camera footage that has been aired by Iran’s state broadcaster and reviewed by NBC News.

The grainy and soundless footage does not appear to be obviously manipulated, and appears to cover much of her time inside the station on Sunday, bar a gap of just under 90 seconds before she reaches the turnstiles. 

However, the girl disappears from view during the crucial moment: a four-second period when she actually boards the subway carriage and ends up on the floor.