This bomb addressed to former CIA director John Brennan was mailed to CNN's New York bureau. (ABC News/AP)
Scott Stewart is vice president of tactical analysis for Stratfor Threat Lens and a former special agent with the State Department's Bureau of Diplomatic Security, where he was involved in hundreds of terrorism investigations.

Law enforcement authorities arrested a man in Florida on Friday morning in connection with the suspected pipe bombs sent to several prominent Democrats and other critics of President Trump this week. The devices have shocked and scared people around the country, even though none of them have gone off and no one has been injured or killed.

And from the evidence available publicly so far, panic — but no actual explosions — may be exactly what the person behind them wanted.

I am a trained post-blast investigator who has worked many bombing cases, including the 1993 World Trade Center bombing and the first al-Qaeda bomb attacks against the United States, in Yemen in 1992. To me, the images and other details released regarding these devices make it very clear that they were intended more to alarm than harm.

They are very small; constructed using 6-inch lengths of 1-inch PVC pipe that was filled with low-explosive powder. Had one of these devices detonated, it could have caused injury, but unlikely to have killed anyone. By way of comparison, these bombs are smaller than the pipe bombs Unabomber Ted Kaczynski made — and he used metal pipe. Even so, of Kaczynski’s 16 devices, only three resulted in fatalities.

Unlike the Unabomber packages, which were cleverly disguised so that recipients might actually open them, these current devices were mailed or delivered in padded manila envelopes with very little effort to disguise their contents. Unlike most traditional letter or package bombs, these devices did not contain any sort of trigger to activate the bomb when the envelopes were opened. Instead, they had a digital clock affixed to them that was presumably intended to function as a timer to detonate them at a specific time and date — although since none of them have gone off, it is unclear at this point if the timers were properly wired to detonate the bombs when the alarm activated, or if they were even set.

All the devices in the images that have been released look like a stereotypical bomb, including the big digital timer with numbers on the front. The timer was really much bigger than needed. The design of these devices appeared to have serious flaws, including the battery size and the gauge and length of the wire used. I am skeptical that these could have actually functioned at all, as are many other experts. The FBI explosives laboratory will examine the recovered devices and will soon determine conclusively whether they could have detonated.

Whether they worked, they do appear to have all the components required to meet the definition of a bomb under the legal definition of a destructive device. This means the alleged bombmaker is likely to face the full force of the law, as he should. Despite the design flaws, black powder can be volatile and the devices could have detonated due to static electricity or friction, and sending devices intended to terrify people rather than kill them is still an act of terrorism.

The envelope addressed to former CIA director John Brennan and sent to CNN also contained a small envelope of as-yet-unidentified white powder that the New York Police Department reports was not biologically harmful. We’ve seen unknown thousands of hoax white powder letters in the years since the 2001 anthrax letters, mailed by people seeking to scare and disrupt. Finally, there was also a faux Islamist militant flag sticker affixed to the outside of the PVC pipe on the first bomb sent to CNN. It is unclear if such stickers were affixed to the others, but it is quite likely. This sticker was of a design that is popular among some on the far right, along with some other as-yet-unidentified images. Like the big ticking clocks, these elements all appear almost too well-staged. Based on my experience, it appears that the envelope of white powder and the stickers were intended to be seen, to send a message and create panic. I do not believe the bombmaker added them so that they would be destroyed in a subsequent explosion.

This all suggests the devices were not intended to detonate, but to be discovered and create panic and mayhem. What better way to ensure your prop devices receive lots of attention than sending them to prominent individuals, such as a former president and a former secretary of state, and a media company?

The big outstanding question now is what was the bombmaker’s motive? Was this an attempt to threaten and intimidate prominent Democrats or critics of Trump? Was it — as some Trump supporters are openly speculating — an attempt to make Trump supporters look like they were violent terrorists? Or was some third party doing it to further inflame the bitter partisanship currently wracking the United States? Certainly, the bombs have achieved this, even if that was not the objective of the author of these attacks.

Why would someone interested in terrifying the public or making a statement send a bomb that might or might not even have been capable of exploding, rather than just sending devices that would actually detonate?

It could be that the bombmaker wanted to send working bombs but failed. Crafting an effective letter bomb is far more difficult than making the crude pipe bombs involved in this case and requires more skill. It could also be that the bombmaker wanted the bombs to be found: If the motive really was to implicate an innocent party by making a device with false indications of the sender’s ideological bent, it would make sense to leave those intact rather than destroy them in an explosion. Finally, some attackers simply believe they can achieve their objectives with a threat rather than violence. My Stratfor colleague Fred Burton and I were involved in helping authorities track down bombmaker John Patrick Tomkins, “The Bishop,” who sent a series of complete, but unassembled, pipe bombs to financial services companies in a failed effort to manipulate specific stocks to a predetermined price for financial gain. He had initially sent threatening letters in 2005, and when those didn’t work, he sought to increase the pressure on the firms to meet his demands by sending bombs.

With the amount of forensic evidence left in the 12 unexploded devices recovered so far, it was no surprise that the arrest came quickly. Now the answers to the many questions the bombs have raised may soon follow.