Luke 23:21

But they shouted

(ο δε επεφωνουν). Imperfect active of επιφωνεω, to call to. Old verb and a verb pertinent here. They kept on yelling.Crucify, crucify

(σταυρου, σταυρου). Present active imperative. Go on with the crucifixion. Mark 15:13 has σταυρωσον (first aorist active imperative), do it now and be done with it. No doubt some shouted one form, some another.