Multiple officials and terrorist experts suspect the man threatening vicious attacks against the United States in a purported terror tape is Adam Yahiye Gadahn (search), a young American who converted to Islam.
Their suspicions were echoed by the director of a California mosque, who told FOX News on Friday he also believes Gadahn is the man in the mysterious video.
Haitham Bundjaki, the Orange County imam who converted Gadahn to Islam and whom Gadahn later assaulted, said outside his mosque that it sounds like Gadahn on the tape.
In the video, aired Thursday night by FOX News, a man wearing dark glasses and an Arab headdress wrapped around his face claims to be an American member of Al Qaeda and promises attacks that will make the streets of America "run red with blood."
From the gestures and voice, Bundjaki told FOX outside his Garden Grove Mosque where Gadahn became a Muslim, "I believe it was Adam."
Some U.S. officials had already speculated that the voice might belong to Gadahn, who also goes by the names Adam Pearlman and Abu Suhayb Al-Amriki.
In May, the FBI announced that Gadahn had ties with senior Al Qaeda lieutenant Abu Zubaydah in Pakistan, and that he had attended terrorist training camps in Afghanistan and served as a translator for the terror network.
"The magnitude and ferocity of what is coming your way will make you forget all about September 11th,” the man calling himself "Azzam the American” says on the video. “After decades of American tyranny and oppression, now it's your turn to die. Allah willing, the streets of America will run red with blood, matching drop for drop the blood of America's victims.”
Gadahn's aunt, Nancy Pearlman, told FOX News in an interview that the FBI had shown her a few minutes of the same video a couple nights ago, but she couldn't be sure whether it was her brother's son speaking or not.
"It could be him, but it might not be," Pearlman told FOX. She said the FBI told her they'd be showing the video to her brother within 24 hours.
It was hard to pinpoint the voice as Gadahn's on the video, in which the nearly fully covered, bespectacled speaker gestures animatedly and points directly at the camera, because the family hasn't seen or heard from him in years, said Pearlman.
"All communication was lost with him about three years ago," she told FOX. "He stopped calling us and he stopped e-mailing us."
During the last contact, the family assumed Gadahn was in Pakistan based on things he alluded to, and believed he'd married an Afghan refugee.
According to a U.S. official, the tape was also being shown to detainees to help identify the speaker. A U.S. official told FOX News the tape is believed to be authentic. But the CIA says it has been unable to confirm the tape's authenticity and is analyzing it further.
The tape bears the logo of the As-Sahab Production Committee, which has produced previous Al Qaeda tapes.
FOX News obtained the videotape independently of ABC News, which also aired portions of the video Thursday night.
News broke Wednesday that ABC had the tape and had provided it to federal officials, but the network decided not to air it immediately because a preliminary CIA analysis was unable to determine if it was legitimate.
The tape was handed to the CIA and National Security Agency by ABC News three days ago, multiple government sources told FOX News. ABC is said to have received the tape last weekend from a terrorist source in Waziristan, a region in Pakistan near the Afghan border where the Taliban and Al Qaeda are believed to be holed up.
"We cannot verify the authenticity of this tape," one official said after the preliminary technical analysis presented inconclusive results. One source said the verification process had been complicated because the tape is a copy, not an original.
In the 75-minute message, the speaker praises the Sept. 11 attacks, calls Usama bin Laden and his deputy his leaders, and says a new wave of attacks could come at any moment.
The speaker claims the United States is his country of origin but does not say specifically where he lives. He speaks both Arabic and English with an international accent that is hard to characterize, an intelligence official said.
"The video content is classic Al Qaeda propaganda, in terms of anti-U.S. ideology and denunciation of the U.S.," a U.S. official told The Associated Press.
The official also said the video appears to have been made in the last several months, perhaps as recently as late summer, because of references to the conflict in Darfur, Sudan, the Sept. 11 commission and the same-sex marriage issue.
FOX News’ William LaJeunesse, Catherine Donaldson-Evans, Rita Cosby and The Associated Press contributed to this report.