This is the 14669th most frequent Russian word.
перепугали
"Scared badly" or "frightened."
The word 'перепугали' is used to describe that the action of shouting excessively caused fear to all the children.
Они так громко закричали, что перепугали всех детей.
They shouted so loudly that they frightened all the children.
Here, 'перепугала' expresses the intense fear caused by a scene from the horror show.
Сценка из ужастика в клубе перепугала не только меня, но и моих друзей.
A scene from the horror show in the club terrified not only me, but also my friends.
In this context, 'перепугал' indicates an intense, sudden fear reaction in the dog.