Coincidence? Or are CBS late-night talk-show hosts being targeted by terrorists?
"It would be too early to link these incidents," said Laura Eimiller, the spokewoman for the FBI's Los Angeles office, which is investigating the Ferguson case along with the Los Angeles Police Department.
That said, Eimiller added, "Of course, [looking into a link] would be part of any investigation."
The Letterman threat was posed in the form of a diatribe on a Website that is a so-called "clearing house for al-Quaeda material." Its author was supposedly angry over a Late Show joke. Letterman responded on Monday's show by cracking more jokes.
A day later, Ferguson wasn't laughing when his Late Late Show received a letter containing a powdery substance feared to be anthrax. Initial tests determined the deadly toxin was not present.
Eimiller said terror scares, like Fergson's, are not uncommon.
Neither are incidents spurred by other incidents, like, say, Letterman's.
"Unfortunately," Eimiller said, "news accounts do inspire copycats."
For now, both cases are definitely not closed.