{The place was shaken} (esaleuth(8820)ho topos). By an
earthquake most likely as in  16:26 , but none the less a token
of God's presence and power ( Ps 114:7  Isa 2:19,21  Heb
12:26f. ). {Were gathered together} ((8873)an sun(8867)menoi).
Periphrastic past perfect passive of sunag(935c). {They spake}
(elaloun). Imperfect active indicative, began to speak, after
being filled (epl(8873)th(8873)an, aorist passive indicative) with the
Holy Spirit. Luke uses the very words of the prayer in verse  29 
to describe their conduct.