South Africans have killed at least 22 foreigners and terrorized many times more in the past week as a wave of xenophobia washes over the country. See photos here. Anger against immigrants is not new to South Africa, but the violence rarely reaches this level.

Nobel Peace laureate Desmond Tutu condemned the attacks: “Please stop. Please stop the violence now. This is not how we behave. These are our sisters and brothers. Please, please stop,” he said, as quoted in the Cape Times.

The violence has been targeted at refugees and immigrants who fled Zimbabwe, Mozambique, Somalia and other African nations to find safety and jobs in their new home. But South Africa itself has been struggling with 40 percent unemployment and rampant crime. Marketplace reporter Gretchen Wilson has a powerful story on how the violence is tied to the country’s economic problems.