Also tonight, regret from a woman who sparked a twitter backlash over an offensive tweet that joked about aids in south africa. She says she's sorry. But so many are wondering how a public relations... See More
Also tonight, regret from a woman who sparked a twitter backlash over an offensive tweet that joked about aids in south africa. She says she's sorry. But so many are wondering how a public relations executive could spark such a public relations disaster. Abc's gio benitez with that story. Reporter: She's the pr executive at the center of a digital firestorm. Justine sacco now apologizing after this offensive tweet went viral. "Going to africa. Hope I don't get aids. Just kidding. I'm white." In a statement, sacco tells abc news, "words cannot express how sorry I am and how necessary it is for me to apologize to the people of south africa." She was fired saturday from her top pr job at internet giant iac, where she repped some of the biggest names online, like match.Com, the daily beast and about.Com. This is one of the fastest responses and crash and burns I've ever seen from a tweet. Reporter: Sacco posted the tweet friday, just before a nearly 12-hour flight from london to cape town, south africa. While she was apparently offline in midair, millions were online, anxiously waiting for her to land and see the uproar her tweet caused. The hash tag "has jus titine landed yet" became an instant trend. Her former bosses calling the tweet outrageous and offensive. There are so many teachable moments here. Think before you tweet. And never, never put out something that can be perceived as racist. Reporter: This photo reportedly shows sacco at the south africa airport when she landed. She quickly deleted the tweet and her entire account. She tells us, "it is terribly easy to be cavalier about an epidemic that one has never witnessed first hand. I am ashamed." So many saying tonight she should have known better. Not only because of her job talking to reporters, but because she herself was born in south africa. Tonight, sacco telling us she cherishes her south african ties, rebecca, and that she's very sorry. Gio benitez, thank you.
This transcript has been automatically generated and may not be 100% accurate.