Neither package ever made it to the targeted institutions, but the two intercepted mail bombs have prompted a quick and determined response, both in Chicago and around the world.
The United States Postal Service has announced a suspension of international mail from Yemen, which is believed to be the origin of the cargo bombs, as authorities made at least one arrest and revealed that the terrorists used forged documents and ID cards in the foiled plot.
With extra security present, many of those in Chicago's Jewish community continued their Sabbath, despite word at least one Jewish house of worship may have been the target of a foiled terrorist plot.
"Unfortunately, we have to have it because no one feels safe, really. To stay away, that gives into them, doesn't it?" said Evelyne and Jacques Preis.
ABC7 Chicago confirmed Or Chadash in Edgewater was to be one of the recipients. The small Jewish congregation serves a mainly gay, lesbian, bisexual and transgender community and has about 100 members.
The group's co-president remained both stunned and fearful Saturday and didn't want to appear on camera.
"We don't know how we were located. We don't know if it was local or foreign. We just don't know, and at this point, most of us are feeling that we'd rather not make ourselves personal targets," the co-president told ABC7.
Or Chadash shares facilities with the Emanuel Congregation. The rabbi of that group offered a possible explanation for why they may have been targeted.
"Maybe someone actually knew that and thought, 'Ah, here's a way to get both Jews and homosexuals,'" said Emanuel Congregation's Rabbi Michael Zedek.
"I feel that a threat to a synagogue is a threat to any religious institution in this country. The terrorists that we're dealing with are really attacking the Western culture and the Western world," said Rabbi Michael Siegel of the Anshe Emet Synagogue.
Siegel leads Chicago's Anshe Emet congregation. He said an FBI agent visited his home Friday night to discuss the bomb plot. Siegel tells ABC7 Chicago there is no indication his was the second synagogue that was targeted.
Chicago police did have an officer at the synagogue during Saturday's service.
The bombs were discovered Friday after one had been shipped by Fedex through Dubai and the by UPS via England.
"I can confirm the device was viable and could have exploded," said British Home Secretary Theresa May.Security officials in England say the powder hidden in a toner cartridge inside a shipped computer printer may be the highly explosive PETN, the same used in the failed plots of the so-called 'shoe and underwear bombers.'
Meanwhile Saturday, authorities in Yemen arrested a female suspect who allegedly sent the two shipments. They continue searching for others possibly involved.
"It does contain all the hallmarks of al-Qaeda," said U.S. Homeland Security Sec. Janet Napolitano.
University of Chicago professor and author a new book about terrorism Robert Pape says continued U.S. military occupation of the Middle East fueled the recent plot.
"This is not making us safer. It is fueling the resentment," said Pape. "This time, we were lucky. We may not be lucky in the future."
Last month, U.S. intelligence officials warned that terrorists may try to mail chemical and biological materials as a part of an attack on the United States and other Western countries. Synagogues in the Chicago area were advised Saturday to take appropriate precautions.