I need to extract an unknown word that immediately follows a word then a comma. More preceisely, I want to get the word that comes after post followed by a comma then a space.

Sample string 1:

admin wrote a new post, FIRE 2 days, 2 hours ago

Sample string 2:

admin posted an update 2 days, 3 hours ago

Only the first sample string qualifies and the word FIRE should be returned.