It’s not just high-profile targets that are at-risk, folks.

PORTLAND — A Corvallis teenager was arrested Friday in connection with a car bomb at a Christmas tree lighting event.

The bomb was inert and posed no danger, officials said.

Mohamed Osman Mohamud, 19, a naturalized U.S. citizen from Somalia and resident of Corvallis, was arrested on accusations of attempting to use a weapon of mass destruction (explosives) in connection with a plot to detonate a vehicle bomb at an annual Christmas tree lighting ceremony, the Justice Department announced.

According to the Reuters version of the story, Mohamud used a cell phone to detonate what he thought was van full of explosives. The target was the annual Christmas Tree lighting in the capitol of Portland, Oregon’s largest city (error corrected) during the evening of the busiest shopping day of the year. Mohamud was not aiming for a couple dozen victims, but hundreds and perhaps thousands and his motivation was “violent jihad”.

We shouldn’t fret, though. The authorities already know, scant hours after the arrest, that this was an isolated incident.

Dwight C. Holton, U.S. Attorney for the District of Oregon, said, “This defendant’s chilling determination is a stark reminder that there are people — even here in Oregon — who are determined to kill Americans. The good work of law enforcement protected Oregonians in this case, and we have no reason to believe there is any continuing threat arising from this case.”

That’s all well and good, but do we have reason to believe there isn’t? Have the FBI and the Portland Police Bureau run down all of Mohamud’s friends and associates? Have they brought a few folks in for questioning? Far be it from me to criticize Dwight C. Holton, U.S. Attorney for the District of Oregon, but I’m not confident in any police department’s ability to thoroughly investigate a suspect’s known associates in only a couple or three hours from the point of arrest. I realize this investigation has been ongoing for months, but perhaps the authorities could wait a few days before making the boilerplate “there’s nothing more to see here so move along” announcement, if for no other reason than to assure us that they’re diligently running down every possible lead.

Though the authorities were on top of this one, we should remember that they’re not going to catch every attempt. Mohamud chose Portland because it was an unlikely place for a terrorist strike and you can bet that if this occurred to a teenager on his first act of jihad, then it’s occurred to the seasoned veterans. I have no doubt that, even now, jihadists are looking at places where we gather as good places to strike and the police can’t be everywhere no matter how they may try to reassure us that they’re on top of things.

As we saw recently in Times Square, the most effective anti-terrorist tools are the eyes and ears of a vigilant citizenry. I made this point about airline security in the latest episode of my podcast, The Delivery, and it works outside the airport terminal, too. For every plot our law enforcement agencies foil, there are other plots they know nothing about. We still have to keep our eyes open, even in places where we think we should be safe, like a Christmas Tree lighting.