Adam Gadahn, al Qaeda's English-speaking spokesman who calls himself Azzam al-Amriki, or Adam the America, has become a powerful propaganda tool for the terror organization.
Gadahn resurfaced this week in an al Qaeda video released on the anniversary of the London bombings.
"No sane Muslim should shed tears for them," he said of al Qaeda's Western victims. "And they should blame no one but themselves because they are the ones who started this dirty war."
Gadahn's career as a jihadist seems to be taking off, and his prominent role may signal a change in strategy by al Qaeda as they seek to exploit mistakes by the West and gain new recruits among populations in Europe and the United States. In his last video, Gadahn was filmed without a mask, unlike previous propaganda tapes.
"It shows that they're getting more sophisticated," said Jessica Stern, author of "Terror in the Name of God: Why Religious Militants Kill." "They're getting better at propaganda. That's bad news. The absence of a disguise, to me, shows a new media savvy. It's a transformation in the type of recruit they're aiming at."
Gadahn was last seen in September 2005 when al Qaeda released a video to mark the 9/11 anniversary in which he made threats against Melbourne, Australia, and Los Angeles. Although he is not wanted in connection with any terrorist acts, he is wanted for aiding al Qaeda.
In 2004 former Attorney General John Ashcroft and FBI Director Robert Mueller put him and seven others on a "most wanted list" of people plotting terrorist attacks to upset that year's presidential election.
Gadahn's militancy and hatred of his native country and culture makes many people wonder how a man raised in California became one of the FBI's most wanted terrorists?
Raised on this goat farm near Orange County, he was born Adam Pearlman in 1978. His Jewish father changed the family name to Gadahn when he converted to Christianity.
As a teenager, family members say Adam struggled and turned first to heavy metal music, then to Islam.
Haitham Bundakji, an elder at the Orange County mosque where Gadahn studied his new faith, recalled how the young convert fell in with a group of other men at the mosque who may have been affiliated with al Qaeda.
"He was more to himself than anything else, and he was shy," Bundakji said. "We thought they were studying the Koran, which is our scripture, and things of that nature, and learning about Islam. That's what we thought originally."
Stern, who interviewed many young terrorists for her book, said she found that all felt wronged or humiliated in some way and were searching for an identity.
"Extremist religion provides that," she said. "Everything black and white, either with us or against us. It's very comforting because you don't have to ask yourself, 'Why is my life not living up my expectations?' You can just blame it all on some injustice. That's exactly what he's speaking to."
Gadahn left for Pakistan in 1998. He may have crossed paths with fellow Californian John Walker Lindh, who also joined al Qaeda but was captured by American forces. His family says they had no clue he'd become involved in al Qaeda.
"I am surprised as everyone else," said his father, Philip Gadahn. "Even when he was keeping in touch with us, he would send us a card every six months when he was traveling around."
Now, the only messages from Gadahn are vehemently anti-American statements that encourage violence.
"We love nothing better than the heat of battle, the echo of explosions and slitting the throats of infidels," Gadahn said. "If it's hard to imagine that any compassionate person could see pictures, just pictures of what the crusaders did to those children, and not want to go on a shooting spree at the Marines housing facilities at Camp Pendleton."
Stern said the problem is that Gadahn actually sounds somewhat reasonable. He is speaking about horrible acts that may or may not have been committed by American troops in Iraq, such as the alleged murder of 24 people in Haditha and the alleged premeditated rape of Iraqi woman and the killings of her and her family.
"This is our worst nightmare in a way, because incidents like that play right into the hands of people like this, who will use it as an opportunity to draw new recruits to the jihadi cause," Stern said.
ABC News' Kate Snow contributed to this report.