As he stepped across the threshold, Tommy brought the picture down with terrific force on his head.
( ( As ( he ( stepped ( across ( the threshold ) ) ) ) ) ( , ( Tommy ( ( ( brought ( ( ( the picture ) down ) ( with ( terrific force ) ) ) ) ( on ( his head ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN As) (S (NP (PRP he)) (VP (VBD stepped) (PP (IN across) (NP (DT the) (NN threshold)))))) (, ,) (NP (NNP Tommy)) (VP (VBD brought) (PP (ADVP (NP (DT the) (NN picture)) (RB down)) (IN with) (NP (JJ terrific) (NN force))) (PP (IN on) (NP (PRP$ his) (NN head)))) (. .)))
Tommy stepped across a threshold and put a picture down on his head.
( Tommy ( ( ( ( stepped ( across ( a threshold ) ) ) and ) ( ( ( put ( a picture ) ) down ) ( on ( his head ) ) ) ) . ) )
(ROOT (S (NP (NNP Tommy)) (VP (VP (VBD stepped) (PP (IN across) (NP (DT a) (NN threshold)))) (CC and) (VP (VBD put) (NP (DT a) (NN picture)) (PRT (RP down)) (PP (IN on) (NP (PRP$ his) (NN head))))) (. .)))