Americans reported to have joined al Qaeda:
Adam Yahiye Gadahn (Pakistan)
At age 35, U.S.-born and California raised Muslim convert Gadahn is the only person known to have been charged with treason since the 1940s. He was recruited in Garden Grove outside Los Angeles as a teenager by the Egyptian leader of a sham charity, Hisham Diab, who was affiliated with the "Blind Sheikh" Omar Abdul Rahman, convicted for plotting to attack New York City landmarks, and Abu Zubaydah, the first al Qaeda leader captured by CIA after 9/11. Gadahn traveled to Pakistan and in 2004 appeared masked in an al Qaeda video as "Azzam the American" and threatening his homeland. He has since appeared unmasked in dozens of al Qaeda propaganda videos, notably calling on American admirers of Osama Bin Laden to carry out individual jihad inside the U.S. homeland. However, senior intelligence and counterterrorism officials have consistently said for a decade that despite his role in crafting some of Bin Laden's past speeches and al Qaeda's messaging, Gadahn is not an operational figure involved in planning actual attacks and many sources deny he is on a U.S. targeting list for a drone strike.
Mohammed Bayazid (Sudan)
A charismatic Syrian immigrant to the United States in his teens, Bayazid studied engineering briefly in Kansas City. Inspired by the writings of Palestinian jihadi Abdullah Azzam, the leader of the "Arab Afghans" fighting the Soviets in Afghanistan, he traveled to Pakistan in the late 1980s and fell in with Osama Bin Laden and his group of wealthy Arabs volunteering for the fight across the border, author Lawrence Wright wrote in his 2006 history, "The Looming Tower: Al Qaeda and the Road to9/11." Bayazid was a founding member of al Qaeda but later denied allegations he was involved in such activities as attempting to procure uranium on behalf of Bin Laden to create crude nuclear weapons, according to "Jihad Joe: Americans Who Go To War In the Name of Islam" by author J.M. Berger. But Bayazid, who has in the past occasionally consented to journalists' interviews, is said to be retired from jihad and unlikely to be atop a U.S. kill list, according to a source.
Ahmad Abousamra (Syria)
Born in France and raised in an affluent Boston neighborhood, Abousamra, 33, is a duel Syrian-American citizen and has been charged with providing material support to terrorists. Federal authorities have accused him of traveling to Yemen in 2002 and 2004 for terror training with Tarek Mehanna who was convicted on terrorism charges in 2011. Abousamra left the U.S. in 2006 and the FBI believes he is living with his wife and daughter in embattled Aleppo, Syria, where al Qaeda-linked foreign fighters at war with Syrian leader Bashar al Assad are plentiful.
Jehad Mostafa (Somalia or Yemen)
Born in Waukesha, Wisconsin, the 32-year old is under indictment in in his former hometown of San Diego since 2009 for his alleged involvement with the al Qaeda affiliate al-Shabaab in Somalia, though he may now be in Yemen. In Shabaab, Mostafa acted "as a training camp instructor and a leader of foreign fighters [and] is also skilled in the group's media activities," according to the State Department's Rewards For Justice program. There has been some speculation that a masked American using the nom de guerre "Abu Abdullah al-Muhajir" photographed in Somalia in late 2011 was Mostafa. He gave a recorded speech stating that he was an emissary of al Qaeda leader Ayman al-Zawahiri to bring aid to Somali drought victims on behalf of "the martyr Bin Laden."
Abu Ibrahim Amriki and Sayfullah al-Amriki (Pakistan)
Almost nothing is publicly known about these purported Americans who appeared in two videos posted on jihadi Internet forums four years ago. The bald-headed "Abu Ibrahim Amriki" -- a nom de guerre -- stood in the back of a pickup truck before a crowd of fighters in Pakistan's tribal areas wielding an AK-47 in a 2010 video appearing to be "a leader or a popular figure," according to the Long War Journal, which tracks militancy in the region. In late 2009, "Sayfullah al-Amriki" addressed the same group, the "German Taliban Mujahideen," in English, saying, "We must rush to the lands of jihad. We must travel on the path of Allah. It is an obligation on us; it is not an option. You must fight."
With ABC News Digital Journalist Luis Martinez at the Pentagon.