A naturalized U.S. citizen from Somalia was arrested Friday night after he attempted to bomb a Christmas tree lighting ceremony in Portland, Ore., according to the Justice Department.

The FBI arrested Mohamed Osman Mohamud after he attempted to detonate a van laden with what he thought were explosives parked near the tree-lighting ceremony in Portland’s Pioneer Courthouse Square.

Muhamud, a 19-year-old resident of Corvallis, is scheduled to appear in federal court in Portland on Monday. He faces a maximum of life in prison and a $250,000 fine if convicted of the charge of attempting to use a weapon of mass destruction.

The arrest was a culmination of a long-term undercover operation. The FBI first learned of Muhamud’s plot last year and gave Muhamud the phony bomb. The public was never in danger from the device. When Muhamud tried to detonate it using a cell phone he called the FBI instead.

“While the public was never in danger from the device, this case serves as yet another reminder of the need for continued vigilance both at home and abroad,” David Kris, assistant attorney general for national security, said in a statement.

Even though the bomb was inert, the threat was very real, according to the Justice Department.

In August 2009 Mohamud was in e-mail contact with an associate overseas who is believed to be involved in terrorist activities, according to an affidavit filed in support of the criminal complaint.

In December 2009 when the associate was located in the North West Frontier Province of Pakistan, he and Mohamud discussed the possibility of Mohamud traveling to Pakistan to engage in violent jihad. The associate allegedly referred Mohamud to a second associate overseas and provided him with a name and e-mail address to facilitate the process.

In the months that followed, Mohamud allegedly made several unsuccessful attempts to contact the second associate until an FBI operative contacted him via email in June 2010 under the guise of being the person he was trying to reach.

Mohamud and the FBI undercover operative then agreed to meet in Portland in July 2010. At this meeting, Mohamud allegedly told the FBI undercover operative that he had written articles that were published in Jihad Recollections, an online magazine that advocated violent jihad.

He also indicated that he wanted to become “operational.” Asked what he meant by “operational,” Mohamud stated that he wanted to put an “explosion” together, but needed help.

At a second meeting in August 2010, Mohamud allegedly told undercover FBI operatives he had been thinking of committing violent jihad since the age of 15. Mohamud then told the undercover FBI operatives that he had identified a potential target for a bomb: the annual Christmas tree lighting ceremony in Portland’s Pioneer Courthouse Square on Nov. 26, 2010, according to the affidavit.

The undercover FBI operatives cautioned Mohamud several times about the seriousness of this plan, noting there would be many people at the event, including many children, and emphasized that Mohamud could abandon his attack plans at any time with no shame, according to the affidavit.

“You know there’s gonna be a lot of children there?” an undercover FBI operative asked Mohamud.

According to the affidavit, Mohamud responded that he was looking for a “huge mass that will ... be attacked in their own element with their families celebrating the holidays.”

Further discussing the attack, Mohamud allegedly stated, “…it’s in Oregon; and Oregon like you know, nobody ever thinks about it.”

The affidavit alleges that in subsequent months, Mohamud continued to express his interest in carrying out the attack and worked on logistics.

He allegedly mailed bomb components to the undercover FBI operatives, who he believed were assembling the device. He also mailed them passport photos, as part of a plan to help him sneak out of the country after the attack. In addition, Mohamud provided the undercover FBI operatives with a thumb drive that contained detailed directions to the bomb location and operational instructions for the attack.

On Nov. 4, 2010, Mohamud and the undercover FBI operatives traveled to a remote location in Lincoln County, Ore., where they detonated a bomb concealed in a backpack as a trial run for the upcoming attack, according to the affidavit.

Afterwards, on the drive back to Corvallis, undercover FBI operatives questioned Mohamud as to whether he was capable of looking at the bodies of those who would be killed in the upcoming attack in Portland. According to the affidavit, Mohamud responded, “I want whoever is attending that event to leave, to leave either dead or injured.”

Upon returning to Corvallis that same day, the affidavit alleges that Mohamud recorded a video of himself with the undercover FBI operatives in which he read a written statement that offered a rationale for his bomb attack. On Nov. 18, 2010, undercover FBI operatives picked up Mohamud to travel to Portland in order to finalize the details of the attack.