The vagrant wolfed down the Thanksgiving dinner at the church.
Literal
Vagrant [topic-は] church [at-で] [possessive-の] Thanksgiving dinner [object-を] greedily ate.
がつがつ is a 擬態語 for eating greedily, voraciously. 浮浪者 means 'vagrant/homeless person.' 感謝祭 is 'Thanksgiving' — a Western holiday rendered in Japanese kanji. The mimetic がつがつ vividly conveys desperation.