off / from

English as a Second Language English Vocabulary, Grammar and Idioms
1
  1. I walked till I came within a hundred yards off/from the building. Then a bomb blasted.
    Which preposition (ie) ‘off’ or ‘from’ should I use?
    Thanks.
  2. I walked till I was at a distance of a hundred yards from the building. Then a bomb blasted.
    Does this sentence OK and mean #1?
    Thanks.
2
  1. You can use ‘of’ but not ‘off’.

‘Then a bomb blasted’ should be, ‘then there was a bomb blast.’ in both sentences.
A more literate way of phrasing them would be:
I walked until I was within a hundred yards of the building, then there was a bomb blast.
I walked until I was a hundred yards from the building, then there was a bomb blast.