The case caused a nationwide sensation at the time.
Tips
usage
The 一时 ('for a time') is doing real work: it implies the sensation has faded. 'Made a huge splash - though now largely forgotten.' Use it for past events; for ongoing sensations prefer 轰动全国 or 引起轰动.
grammar
Functions as a predicate (这件事轰动一时) or an attributive (轰动一时的新闻). Not typically modifies a verb adverbially.
