happen in a split second

To occur in an instant; to occur in less than a full second of time. The accident that took my leg happened in a split second, but I've been coming to terms with the effects of it for years. The tornado's destruction basically happened in a split second. I can't believe buildings I saw just a few hours ago have been completely razed. Cherish the moments with those you love and be thankful for everything you have, because tragedy can happen in a split second.