This article was updated on April 30, 2010

EXCLUSIVE: By all appearances, Zachary Adam Chesser was the boy next door. He played football and was on the crew team at one of the best high schools in the country. He even studied Japanese. He was hardly the sort of boy you'd expect would suggest on a radical Islamic website that the creators of the edgy cartoon series "South Park" will be targeted for death.

But Chesser also had a dark side. He was a "loner," a former classmate said, one who frequently drew pictures of Satanic figures in his notebooks and had just a few friends, most of them male.

"He was definitely sort of weird," the classmate told FoxNews.com. "He was very into violent industrial music, borderline Satanic bands and stuff like that. He had dark undertones in his interests."

Two years later, Chesser is literally a changed man. He now uses an alias and has a new set of hobbies. He now likes to be called Abu Talhah Al-Amrikee, and his primary interest in this world appears to be Islamic radicalism.

Last week, Chesser, 20, posted a warning on the website RevolutionMuslim.com following the 200th episode of "South Park," which included a caricature of the Prophet Muhammad disguised in a bear suit. The young man, who just two years ago was studying foreign languages at George Mason University, wrote on the site that Trey Parker and Matt Stone, the cartoon's creators, "will probably end up" like Theo van Gogh, a Dutch filmmaker who was murdered in 2004 after making a film critical of Islamic society.

"It's not a threat, but it really is a likely outcome," Chesser told FoxNews.com from his home in Centreville, Va. "They're going to be basically on a list in the back of the minds of a large number of Muslims. It's just the reality."

Comedy Central declined to comment for this story.

However, in a June 22, 2009, interview, Doug Herzog, the president of MTV Networks, admitted that Comedy Central caved to political and commercial pressure when the channel censored a 2006 episode of South Park featuring Mohammed — and he said if given a chance to do it over again he’d do it differently.

“The real story was the story you know, which is that the guys wanted to depict Mohammed and the network wouldn’t let them. And that was the whole story," Herzog told conservative writer Ben Shapiro, who posted excerpts of the interview Friday on BigHollywood.com. "And while I think if we had to do it all over again we would do it differently, that was the decision we made at the time. And I regret it somewhat but I’ve made worse decisions in my life.”

What seems to bend reality is what has happened to Chesser. The school he attended, Oakton High School in Fairfax County, Va., was ranked the 103rd best high school in the country by Newsweek in his graduating year and was ranked 88th by US News & World Report the year before. Among the schools alumnae is 1984 graduate Michaele (Holt) Salahi, better known as the White House dinner party crasher.

Chesser's background offers nothing to suggest that he would recently have eloped and married a Muslim woman he met in college, a woman who has given birth to their baby boy, according to neighbors. While there is no evidence that Chesser became radicalized while at George Mason, there were "dark overtones in his interests" for years, dating back to his years in middle school and high school.

Chesser's longtime classmate, who requested anonymity, said he did not overtly express an interest in converting to Islam while in high school. But given Chesser's past as a loner who sought to create conflict, she said she was hardly surprised to learn what's become of him.

"I was initially pretty surprised because you never suspect someone you've known for so long to put out something like that," she said in reference to Chesser's web posting. "But once I thought about it, I wasn't really surprised. There was definitely a 'loner thing' about him. He had an interest in being controversial and saying crazy things."

Chesser's interests -- hardcore industrial music, Goth and Satanic materials -- appear to have translated "pretty well to violent extremism," the classmate said.

[UPDATE: In the original publication of this article on April 23, it was reported that Chesser lives with his mother, brother, wife and son in Centreville. Chesser's mother, Barbara Chesser, says her son, daughter-in-law and grandson live in another town in Fairfax County. She says that her son has not lived with her since August 2008 and that her daughter-in-law and grandson have never lived with her.]

His parents are divorced, but they maintain an amicable relationship. His involvement in Revolution Muslim is largely unknown in his hometown, neighbors told FoxNews.com.

"They're very isolated people," said a neighbor who requested anonymity. "His mother is very friendly, though. They say 'hi' when I see them, but they don't get personal with anybody."

The neighbor, a devout Christian, said she was scared and surprised to learn that Chesser has posted messages calling for the murder of Jews and, most recently, the deaths of Parker and Stone.

"You have me sweating here," she told FoxNews.com. "I think he's really brainwashed to even think something like that. His family is not violent at all.

"I am so shocked. I really think he had to have been brainwashed into something like that. Zac was a very nice boy. I would never have even associated him with something like this, to do anything harmful."

She said she will maintain more of a distance from the Chessers now, "because we're Christians…. It's kind of sad that American people are falling into this. It's sad that he would be influenced to try to hurt people."

Richard Kolko, a spokesman for the FBI, declined to confirm or deny that the bureau is investigating Chesser's post or Revolution Muslim. He said the FBI will continue to investigate threats made on the Internet to determine if potential exists for those threats to be carried out. NYPD Police Commissioner Raymond Kelly has said law enforcement officials in New York, where the group is based, do not consider last week's posting "as is currently assessed" to be a crime.

But the Anti-Defamation League's Center on Extremism has had the group on its radar since its inception in 2007, Director Oren Segal told FoxNews.com.

"This is just the latest in a long line of threats coming from Revolution Muslim," said Segal, who noted a poem posted on the site in October asking God to kill all the Jews.

While the group has only about 12 members, Segal said a "leadership vacuum" has allowed Chesser to become an emerging figure in the fringe fundamentalist organization, which has staged protests at New York mosques. And he said he is worried that Chesser's post may incite others to violence.

"The group itself is a relatively small group, but the reach this group has by posting materials online is virtually limitless," Segal said. "You never know who is going to react to this type of material or carry out some sort of attack based on what they're reading. Frankly, I don't think we have the luxury to dismiss this type of rhetoric."

He said the ADL has learned that Chesser is interested in starting a Revolution Muslim chapter in nearby Washington.

Ibrahim Hooper, a spokesman for the Council on American-Islamic Relations, characterized Revolution Muslim as a loosely-organized group with such outrageous beliefs he believes it may be a "setup" to smear Islam.

"They say wild and irresponsible things periodically," Hooper told FoxNews.com. "There's a strong suspicion that they're merely a setup to make Muslims and Islam look bad. They say such wild and crazy things that you have to wonder."

Chesser, for his part, declined to indicate exactly what led him to join the group. A faculty member for George Mason University's Muslim Student Association said he had no knowledge of Chesser, who began attending the school in fall 2008 before dropping out in his second semester.

Reached by FoxNews.com via e-mail on Thursday, Chesser said one of his goals in writing for the group is to "raise awareness of the correct understanding of key Islamic beliefs." But he also warned: "If you kill us, then we kill you."

"I seek to help the world understand that neither the Muslims in general nor the mujahideen including Al Qaeda are abject to peace, but that this peace come with the following conditions: a complete withdrawal of non-Muslim forces from Muslim lands, an ending of the propping up of the apartheid regime of Israel, and a ceasing of the propping up of the brutal dictators we currently have who refuse to rule by divine law," Chesser's e-mail read.

"I also seek to help the world understand that there will be no peace until the above conditions are met. Basically the formula works like this … if you kill us, then we kill you. If you do not kill us then we can have peace. 9/11 had nothing to with freedom or democracy. It had to do with the murder of hundreds of thousands of Muslims around the world by American and other powers."

In a separate post on RevolutionMuslim.blogspot.com, which now serves as the group's main website since RevolutionMuslim.com has been shuttered, Chesser quoted Usama bin Laden when referencing why reactions are required when anyone insults or belittles the Prophet Muhammad.

"As Usama bin Laden said with regard to the cartoons of Denmark," Chesser wrote, "'If there is no check in the freedom of your words, then let your hearts be open to the freedom of our actions.'"