The Greek that is often translated as “amazed” in English has the option of various terms in Luang with different shades of meaning.
For Acts 3:10 and 9:7, ema rtaplelleltarga (“as if they could not speak”) was chosen. This is used for “surprise causing introspection about the meaning of what has occurred and what effect it will have.”
For Mark 16:5, hnedu (“surprised”) was chosen. This is used for “surprise causing a physical jerk of the body.”
Source: Kathy Taber in Notes on Translation 1/1999, p. 9-16.