Stop/halt somebody in their tracks
Definition 1 of 2
Pro Tip 1/3Strong Impact
Use when something has a powerful effect that causes a person to pause suddenly. 
Her performance was so moving, it stopped everyone in their tracks.
Pro Tip 2/3Emotional Reaction
Often relates to a sudden emotional reaction such as shock, awe, or fear. 
When the verdict was read, the silence that followed stopped us in our tracks.
Pro Tip 3/3Unexpected Events
Best used in scenarios where the cause of stopping is unforeseen. 
The deer leaping onto the path stopped the cyclist in his tracks.