(S (S (S (BASENP (JJ Small) (NNS explosions)) (VP (VBD were) (VP (VBN heard) (ADVP (RB soon) (RB after))))) (CONJP (COMMA ,) (CC and)) (S (NP (BASENP (NN CS) (NN gas)) (CC and) (BASENP (NN stun) (NNS grenades))) (VP (VBP are) (VP (ADVP (RB also)) (VP (VBN believed) (S (VP (TO to) (VP (VB have) (VP (VBN been) (VP (VBN used))))))))))) (PERIOD .))