The Irish-English past tense of "to be" is peculiar, a vestige of Gaelic Irish.
In the simple past tense, the Irish say "he is after [doing something.]" "He's after writing a letter" is equivalent to "he wrote a letter."
In the "recent news" past tense, the Irish say "I'm only after [doing something.]" "I'm only after getting here" means "I just got here."
In the "perfect past tense," (he had done something,) the Irish would say "he was after doing something."