previously

Previously means before the time being talked about. Previously employed there, as previously stated, previously unknown.

It sets an earlier point against the present narrative and is common in reports, television recaps and formal writing. Previously to is not used — before is the preposition, and previously is the adverb. Note previously unpublished and previously unknown, which are near-fixed phrases in academic and news writing, and that previously is more formal than before and less formal than heretofore.