Jarret Brachman, author of Jihadism: Theory and Practice, talks to host Michele Norris about suspected Fort Hood shooter Nidal Hasan's contacts with Anwar al-Awlaki, a radical imam who now lives in Yemen. He says communications between them should have raised huge red flags. He talks about who al-Awlaki is, and his influence on young, hard-line, English-speaking jihadis around the world.