Audio Recording: One of Us

On July 22, 2011, Anders Behring Breivik set off a bomb outside the Norwegian prime minister's office in central Oslo, killing eight people. He then drove to the island of Utøya, where he killed sixty-nine more, most of them teenagers. In her new book One of Us, journalist Åsne Seierstad tells the story of this terrible day, Norway's own September 11. She delves deep into Breivik's childhood, showing how a hip-hop and graffiti aficionado became a right-wing activist and then an Internet gamer and self-styled warrior who believed he could save Europe from the threats of Islam and multiculturalism.

How did Breivik, raised by a single mother in one of the world's most famously tolerant and egalitarian societies, become convinced that feminism and immigration has destroyed European culture? How did a gifted child from an affluent Oslo neighborhood become Europe's most reviled terrorist?

We spoke with Åsne Seierstad and The New York Times's Lydia Polgreen about the psychological roots of right-wing extremism and about Norway's struggles to come to terms with homegrown terror.