Los Angeles: A 19-year-old Somali-American will appear in court in Portland, Oregon, on Monday charged with "attempted use of a weapon of mass destruction."
Mohamed Osman Mohamud was arrested on Friday after trying to set off what he thought was an explosives-laden van parked near the tree ceremony in Portland`s Pioneer Courthouse Square.
But the device was, in fact, a fake supplied by undercover agents from the FBI who had contacted Mohamud months before and pretended to be accomplices in the plot.
"The threat was very real. Our investigation shows that Mohamud was absolutely committed to carrying out an attack on a very grand scale," said FBI special agent Arthur Balizan.
The Federal Bureau of Investigation (FBI) and local police are also investigating an predawn fire Sunday that gutted a room of a mosque attended by Mohamud in his home town of Corvallis, Oregon.
The overnight blaze "appears to have been intentionally set," said the town`s fire department.
The mosque`s imam Yosof Wanly said he knew Mohamud, who began attending 18 months ago but not regularly. "It`s unfortunate because he is bringing attention to Islam in a negative way, he told local CBS affiliate KVAL.
According to court documents, Mohamud exchanged emails with a contact in Pakistan`s northwest frontier province late last year, and discussed the possibility of Mohamud traveling to Pakistan to engage in jihad.
In June this year an FBI undercover agent contacted Mohamud -- a naturalized US citizen and former student at Oregon State University -- pretending to be an associate of his Pakistani contact.
After meeting the agent in Portland in July, he said he had been thinking of conducting a holy war against infidels since the age of 15, and suggested the plot to bomb Friday`s traditional pre-Christmas ceremony in the Oregon capital.
FBI operatives cautioned Mohamud several times about the seriousness of this plan, noting that there would be many children at the event.
But Mohamud responded that he was looking for a "huge mass that will... be attacked in their own element with their families celebrating the holidays," the documents noted.
"It`s gonna be a fireworks show,... a spectacular show," he was quoted as saying.
Referring to the September 11, 2001 attacks on the US, he also told undercover agents: "Do you remember when 9/11 happened, when those people were jumping from skyscrapers?... I thought that was awesome."
Earlier this month, Mohamud and the undercover FBI operatives traveled to a remote location in Lincoln County, Oregon, where they detonated a bomb concealed in a backpack as a rehearsal of the upcoming attack.
"I want whoever is attending that event to leave, to leave either dead or injured," Mohamud said of the Christmas tree ceremony, according to the court documents.
That same day, he recorded a video, in which he read a written statement that offered a rationale for his bomb attack.
On Friday afternoon, hours before the planned attack, Mohamud met the undercover agents to make the final preparations.
"Mohamud went and looked at the bomb, which was in the back of a large white van. When Mohamud saw the bomb, he told the (undercover agents) it was `beautiful`," said the affidavit.
He was arrested shortly after trying to detonate the fake bomb as the Christmas tree ceremony got underway.
"As Mohamud was transported from the arrest location he yelled `Allahu Akhbar` and began violently kicking the agents and officer in the transport vehicle and had to be restrained," read the affidavit.
Mohamud is due in court in Portland at 1:30 pm (2130 GMT) on Monday.