"paralyzed because of strong emotion" Is there an idiom or fixed-phrase which conveys this meaning?

I'm looking for an idiom or fixed phrase meaning someone was paralyzed with the horror of a sight.

context:

• An old lady sees a young girl run over by a truck.
• A middle-aged man sees his neighbor's teenage son be struck by lightning.

Not looking for a single word (there are too many of them) and it would fit a sentence like "He/She became/was/got/etc______________________."

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

Be like a deer caught in the headlights - to be so frightened or surprised that you cannot move or think.

Each time they asked him a question he was like a deer caught in the headlights.

From Cambridge Idioms Dictionary, 2nd ed.

To be Petrified is to be paralyzed or shocked into inaction by fear or horror.

"The old lady was petrified with horror at the sight of the girl going under the wheels of the truck."