FBI via Getty Images
One of the package bombs that was sent to a critic of President Trump is shown. Experts say excessive postage is a key sign of a suspicious package.
FBI via Getty Images
As the hunt intensifies to try to find who sent at least 10 potentially explosive devices to Democrats and critics of President Trump around the country, a second important question lingers: how exactly were the dangerous packages sent?
The FBI and the investigative arm of the U.S. Postal Service, the U.S. Postal Inspection Service, both declined Thursday to confirm to NPR how the packages reached the destinations at which they were intercepted.
But a look at where they were intercepted indicates at least seven of the 10 were handled by the Postal Service. For instance, two of the packages, addressed to Joe Biden, were found in postal facilities in Delaware. The packages addressed to Hillary Clinton and Barack Obama were intercepted in Secret Service mail screening centers.
The delivery methods are still unclear for the packages addressed to Robert De Niro and CNN, which were both received in Manhattan, and the package addressed to and received at George Soros' home, in Westchester County, N.Y.
"I'm not gonna get into where we think the packages came from," said FBI Assistant Director in Charge William Sweeney, boss of the New York Field Office. "Some were delivered through the postal system."
Why would pipe bombs be able to travel any distance at all through the mail?
That answer too remains unclear.
The USPS does have screening processes in place. In a statement, the service said it uses a combination of "specialized technology, screening protocols, and employee training."
But separately, the U.S. Postal Inspection Service website says "the overwhelming volume of mail does not permit the Postal Service to screen every piece."
In terms of spotting the seven packages in question, mail that weighs more than 13 ounces is not supposed to be delivered using just stamps and anonymous drop-off; a person hoping to send such a package is supposed to have to go into a post office and interact with a USPS employee. It's not clear whether the bomb packages weighed more than 13 ounces.
While most of the packages were caught in transit, at least one, to Rep. Debbie Wasserman Schultz, D-Fla., was successfully delivered on Wednesday. The package was originally addressed to former attorney general Eric Holder, but Schultz' office was listed as the return address.
It was delivered there, and her office was evacuated. Schultz said she was "deeply disturbed by the way my name was used."
Anthony May, a former bomb technician for the Bureau of Alcohol, Tobacco, Firearms and Explosives, said the exterior of the packages had obvious red flags that postal workers should be looking out for, including too much postage and misspelled names.
"If it's got excessive stamps on it, the post office is not supposed to deliver that," May said.
Danger in context
While bombs may not usually be sent to such high-profile targets, the USPIS does investigate an average of 16 mail bombs annually.
"By contrast, each year, the Postal Service processed over 170 billion pieces of mail," the USPIS says on a portion of its website dedicated to mail bomb information. "That means during the last few years, the chances that a piece of mail actually contains a bomb average far less than one in 10 billion!"
In fiscal year 2017, the agency opened 19 investigations related to "suspicious substances and items," which includes bombs, explosives and chemical weapons. The agency made 11 arrests and garnered 20 convictions.
There are no indications at this point that the Postal Service plans to make any policy changes in the short or long term related to suspicious packages.
A spokesperson for the American Postal Workers Union told NPR that although much of the media attention this week has been focused on the public figures the packages were addressed to, it's often forgotten that workers are in danger too.
Two postal workers died in 2001 when anthrax was sent through the mail, a crime that may have been committed by Army biologist Bruce Ivins.
"The reality is, there are a lot of people along the way," the APWU spokesperson said. "They're all certainly at risk here too."