But they shouted (hoi de epephōnoun). Imperfect active of epiphōneō, to call to. Old verb and a verb pertinent here. They kept on yelling.
Crucify, crucify (staurou, staurou). Present active imperative. Go on with the crucifixion. Mar 15:13 has staurōson (first aorist active imperative), do it now and be done with it. No doubt some shouted one form, some another.