Type ‘‘Anwar al-Awlaki’’ into YouTube’s search bar, and you get 40,000 hits. Most of them bring up the earnest, smiling face and placid voice of the first American citizen to be hunted and killed without trial by his own government since the Civil War. Here is Awlaki on what makes a good marriage; on the nature of paradise; on Jesus Christ, considered a prophet by Muslims; on tolerance; on the holy month of Ramadan; and, more quirkily, on ‘‘obesity and overeating in Islam.’’ Here is Awlaki, or Sheikh Anwar, as his many admirers still call him, easily mixing Quranic Arabic with American English in chapters from his 53-CD series on the life of the Prophet Muhammad, once a best seller among English-speaking Muslims.

But in the same queue of videos is material of an altogether different nature. You will find Awlaki explaining why you should never trust a non-Muslim; how the United States is at war with Islam; why Nidal Hasan, who fatally shot 13 people at Fort Hood, and Umar Farouk Abulmutallab, who tried to blow up an airliner over Detroit, were heroes. There is, finally, his culminating ‘‘Call to Jihad,’’ recorded in 2010 when he was already on President Obama’s kill list and on the run in Yemen’s tribal badlands. In it, with the confidence and poise of a YouTube handyman explaining how to caulk a window, he details just why, exactly, it is every Muslim’s religious duty to kill Americans.