horror-struck       
adjective [ after verb ] uk/ˈhɒr.əˌstrʌk/ us/ˈhɔːr.ɚˌstrʌk/ (also horror-stricken)
 极为震惊的;极为惊恐的
extremely shocked and frightened
  They watched, horror-struck, as the car came off the road. 他们惊恐地看着那辆汽车冲出公路。 
 Synonym: horrified