stop dead in tracks
stop (dead) in (one's) tracks
To stop at the exact spot where one is and hold motionless. We stopped dead in our tracks when we heard rustling in the bushes just off the trail. The kids were running along the lawn when the sound of a loud motorcycle stopped them in their tracks.
stop dead in one's tracks
Fig. to stop completely still suddenly because of fear, a noise, etc. I stopped dead in my tracks when I heard the scream. The deer stopped dead in its tracks when it heard the hunter step on a fallen branch.