when the bullets start to fly , your first instinct is to duck 
(ROOT (S (SBAR (WHADVP (WRB when)) (S (NP (DT the) (NNS bullets)) (VP (VBP start) (S (VP (TO to) (VP (VB fly))))))) (, ,) (NP (PRP$ your) (JJ first) (NN instinct)) (VP (VBZ is) (S (VP (TO to) (VP (VB duck)))))))
(ROOT (S (SBAR (WHADVP (WRB )) (S (NP (DT ) (NNS )) (VP (VBP ) (S (VP (TO ) (VP (VB ))))))) (, ) (NP (PRP$ ) (JJ ) (NN )) (VP (VBZ ) (S (VP (TO ) (VP (VB )))))))