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"Bravo 6, this is Sierra 1, two hostiles on top floor of your building. Taking the shot."

— Sierra 1 preparing to take down two terrorists

Sierra 1 is an SAS sniper unit that appears in Call of Duty: Modern Warfare 3 in the mission "Mind the Gap" and gives fire support to Wallcroft and the rest of Bravo 6. After they kill the two men on the top floor, they go to the roof of their building and go prone and still provide fire support but do not move from their position.