stop in tracks
stop (dead) in your tracks
to suddenly stop moving or doing something When I heard the loud scream, I stopped dead in my tracks.Related vocabulary: stop short
Usage notes: often used in the forms stop someone (dead) in their tracks or stop something (dead) in its tracks: The memo was supposed to stop the protest in its tracks.
stop (somebody) in their tracks
if something stops someone in their tracks, or if they stop in their tracks, they suddenly stop what they are doing because they are so surprised A loud scream stopped me dead in my tracks. He opened the door and stopped in his tracks. A complete stranger was sitting in his office.