The idiom stop dead in one's tracks seems to fit. The in one's tracks refers to "on the spot" or "where one is at the moment"; it was first recorded in 1824.
Fig. to stop completely still suddenly because of fear, a noise, etc.
(McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.)
I stopped dead in my tracks when I heard the scream (CDO)
The idiom is a variant of stop cold, and stop dead.
He was so surprised to see them in the audience that he stopped dead in the middle of his speech
Related to the theme of being paralysed through extreme fear are the participles frozen and froze, the verb is often used to express sudden shock, horror, motionless or panic at something, which renders the person affected incapable of taking appropriate action.
All the following examples are taken from Dictionary.com
- I froze in my tracks
- The child was frozen with fear
- My heart froze when she told me the news
- Terror froze him to the steering wheel.
- The lifeguard should have dived in for the boy, but she froze