A.T. Robertson Commentary Luke 24:5

"and as they were affrighted and bowed down their faces to the earth, they said unto them, Why seek ye the living among the dead?" — Luke 24:5 (ASV)

As they were affrighted (εμφοβων γενομενων αυτων). Genitive absolute with second aorist middle of γινομα, to become. Hence,

when they became affrighted . They had utterly forgotten the prediction of Jesus that he would rise on the third day.