PORTLAND -- Some Oregonians question why the FBI let the investigation against Mohamed Osman Mohamud, 19, play out for as long as it did, culminating in a fake bomb at Pioneer Square Park.
Mohamud was arrested at 5:40 p.m. Friday in Northwest Portland and accused of attempted use of a weapon of mass destruction.
The U.S. Attorney's office alleges that Mohamud carried out a protracted plan to detonate explosives in a van parked at Pioneer Square, which was crowded with revelers there for a tree lighting ceremony.
From the time FBI undercover agents first contacted Mohamud to the time he dialed the cell phone thinking he was blowing up Pioneer Square was about 18 months.
On Monday, Attorney General Eric Holder said Monday that federal agents acted properly. Once the undercover operation began, the suspect "chose at every step to continue" with the bombing plot, said Holder. "He was told that children -- children -- were potentially going to be harmed," the U.S. attorney general added.
The police can't arrest someone for saying "I think it would be a great idea to blow up people at Pioneer Square," said Lewis & Clark Professor Tung Yin, who teaches terrorism and the law.
"At that level, it's maybe just a thought crime," he said, "It's a bad thought. Lots of people say dumb things."
Police needed to take several steps to confirm that intent, he said.
Was Mohamud entrapped by the police? No, thinks Yin, who has read a lengthy affidavit explaining the arrest.
The FBI offered Mohamud a variety of chances to do something other than bomb the Square.
"They (the FBI) didn't say 'why don't you do this," Yin explained, "They said 'what do you want to do?"
Yin likened the process to an undercover drug buy, with an officer in plainclothes saying to a potential purchaser "I've got the drugs, if you want to buy them."
The trick, Yin said, is for the police not to coerce the next move. The FBI seemed to avoid that, said Yin, by always offering Mohamud the choice of what to do next.
Mohamud was arrested, Yin pointed out, after he had dialed a cell phone number thinking he had detonated a bomb in van parked at Pioneer Square.
The block was filled with as many as 10,000 people who had gathered for a tree lighting ceremony.
Portland Police Bureau spokesman, Sgt. Pete Simpson said it takes time for investigators to develop proof that the suspect is doing more than just talking big.
"In any investigation, you have certain steps that you can pull the plug and make an arrest, but the charges are different on each time you do that," said Simpson.
"In a case like this they want to show substantial steps toward completing a plan," Simpson said.
"This gentleman made statements about wanting to do something. Those are just words. They gave him the means to continue on with that plan, opportunities to get out," Simpson said, "You let it keep going to see how committed he really is. and are there other people out there? Is he in contact with somebody else that you don't know about."