Walter Harriman came across the pictures of Sgt. Robert Phillips through the SGC data archives. Apparently, Phillips had been part of the team studying the quantum mirror while it was still housed on level 28. Phillips had selected these images from the hundreds taken during the scanning of alternate realities to accompany the report on the mirror to be sent to the Pentagon. However, the report and Sgt. Phillips were lost in an explosion in the labs, so the "true" stories behind the pictures were never revealed.
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