US mail bomb threat: Who was targeted and why

The FBI is investigating mail bombs and suspicious packages that were sent to prominent Democratic critics of President Donald Trump.

Pipe bombs were sent to Barack Obama, other top Democrats and CNN in a coordinated "effort to terrorise" days before polarising US elections. Source: AP

Who was targeted?

The first bomb was discovered Monday in a mailbox at the New York home of billionaire financier and Democratic Party supporter George Soros.

Late Tuesday and early Wednesday, explosive devices were addressed to the New York residence of former Democratic presidential candidate and secretary of state Hillary Clinton; the Washington residence of former Democratic president Barack Obama; Eric Holder, the attorney general under Obama; and John Brennan, Obama's CIA director, sent care of the New York offices of CNN, where Brennan is a frequent guest commentator.

A bomb was found in a mailbox at the suburban New York home of liberal billionaire philanthropist George Soros. Source: AP

Additionally, California Democratic Representative Maxine Waters said the FBI is investigating a suspicious package sent to her. The FBI did not confirm that.

What was in the packages?

The packages confirmed by the FBI were all similar and contained "potentially destructive devices," according to the bureau.

All were wrapped in bubble wrap and placed inside manila envelopes with printed address labels. The envelopes had identical return addresses for Florida Democratic Congresswoman Debbie Wasserman Schultz, the former Democratic National Committee chairwoman.

The devices insides, according to reports and a photograph of one, were small, crude but potentially lethal pipe bombs: usually a metal water pipe filled with explosive material and shrapnel, tightly sealed at the ends and detonated by a fuse inserted through a hole.

New York police commissioner James O'Neill described the one sent to Brennan at CNN as appearing to be a "live explosive device."

O'Neill said that package also contained an envelope of an unidentified white powder.

A screenshot from CNN's Twitter account shows what CNN says is the explosive device that was delivered to their New York headquarters. Source: Twitter

In the case of Clinton and Obama, the US Secret Service said it identified the suspect packages during routine mail screening procedures it provides the former top politicians in facilities separate from their homes.

Bill and Hillary Clinton were both targeted. Source: AAP

The addressees "did not receive the packages nor were they at risk of receiving them," the Secret Service said.

In the case of the package to Holder, it never reached his Washington office. The postal service sent it to the return address: the Florida office of Wasserman Schultz.

Who did it?

So far no suspects have been identified. The FBI said it has sent the packages to its laboratory in Quantico, Virginia for analysis.

"It is possible that additional packages were mailed to other locations," the FBI warned.

What connects the targets?

The targets are all Democrats frequently attacked by Trump online and in speeches as he defends his 2016 election victory and policies he has implemented since coming to office in January 2017.

NYPD officers and emergency services outside CNN's New York office. Source: AP

Obama preceded him in the White House and Clinton was his 2016 election rival. Holder was attorney general in the last years of the Obama administration. 

Trump has labelled CNN the leading purveyor of "fake news" against him, and Brennan is perhaps his most damaging critic from the national security community.

The NYPD Bomb Squad outside the CNN building as officers secure the broadcaster's office, following the discovery of a possible bomb. Source: AP

Trump often ridicules Waters, a senior African-American Democrat, as "low IQ" and has regularly assailed Wasserman Schultz, one of the most senior Democrats in the House of Representatives.