An example of someone who might feel aghast is a person who returns home to find his house has burned down.
Origin of aghastMiddle English agast, past participle of agasten, to terrify ; from a-, intensive + gasten ; from Old English gaestan, to terrify ; from gast, ghost
Origin of aghastMiddle English agast, past participle of agasten, to frighten : a-, intensive pref. (from Old English ā-) + gasten, to frighten (from Old English g&aemac;stan, from gāst, ghost).
(comparative more aghast, superlative most aghast)
From Middle English agast, agasted, past participle of agasten (“to terrify”), from Old English prefix a- (compare with Gothic - (us-), German er-, originally meaning "out") + gæstan (“to terrify, torment”): compare Gothic (usgaisjan, “to terrify”, literally “to fix, to root to the spot with terror”); akin to Latin haerere (“to stick fast, cling”). See gaze, hesitate.