On a Saturday afternoon in September 2013, gunmen from the Somali militant group Al-Shabaab stormed the Westgate Shopping Mall in Nairobi. The siege lasted four days. 67 people were killed, including Ghanaian poet and UN worker Kofi Otieno, a French woman, a Peruvian diplomat and dozens of Kenyans shopping on an ordinary weekend. The attackers asked hostages if they were Muslim before deciding whether to shoot. The scale of the atrocity shocked the world. Kenya's response, military and civilian, showed a country determined not to be broken.