Federal authorities have arrested a man in connection with the mailing of packages containing suspected explosive devices to CNN, top Democrats, and other prominent public figures.
At a press conference on Thursday, officials in NY would not discuss possible motives, or details on how the packages found their way into the USA postal system.
Two officials told The Associated Press that a person working at De Niro's Manhattan office called police after seeing images of a package bomb sent to CNN and recalling a similar package addressed to the actor.
A law enforcement source said the devices appeared to be linked to the others sent to Democratic figures and CNN's New York City hub.
Former CIA director John Brennan, who was the addressee of the pipe bomb sent to CNN, on Thursday assailed Trump for attacking the media.
"We must never allow political violence to take root in America", Trump said at one point.
Authorities who have discovered the parcels around the country - in NY, outside Washington, D.C., in Florida and in Los Angeles - are sending them to the FBI Laboratory in Quantico, Va., for examination there.
DNA found on at least one of the packages, as well as Sayoc's cell phone, helped investigators identify him, multiple law enforcement officials said.
But the twin discoveries led to other undetonated devices being found elsewhere, including in the mailroom at CNN's NY headquarters and a district office of the Florida Democratic congresswoman Debbie Wasserman Schultz.
The first such package had been discovered on Monday at the NY home of George Soros, a billionaire activist known to fund pro-democracy and liberal political groups.
Trump, in a tweet Thursday, blamed the "Mainstream Media" for the anger in society.
Those packages were removed late Thursday morning from DE postal facilities, law enforcement officials said.
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All 10 packages went through the U.S. mail, according to multiple law enforcement officials familiar with the investigation.
In a tweet following the news, Trump wrote, "I will be speaking at the Young Black Leadership Summit in 15 minutes where I will address the investigation into the bomb packages".
The packages stoked nationwide tensions and fears as voters prepared to vote on November 6 to determine partisan control of Congress.
Most of those devices showed the presence of a sulfur substance, which could have exploded, a law enforcement official said.
All of the targets of the IEDs had drawn the ire of President Donald Trump.
Police are now investigating into whether Trump critics or others vilified by the right are being targeted. Brennan advises Trump to "try to act Presidential".
Holder's package was diverted and delivered to Wasserman Schultz's address. Just two days earlier, CNN's offices in NY were evacuated when the package for Brennan, addressed to him at the network, was found in the mailroom. "It has gotten so bad and hateful that it is beyond description".
CNN president Jeff Zucker, whose employees were forced to evacuate their NY bureau on Wednesday by the discovery of the pipe bomb in the mail room, slammed the White House for its "complete lack of understanding" about "the seriousness of their continued attacks on the media". "The president is certainly not responsible for sending suspicious packages to someone no more than Bernie Sanders was responsible for a supporter of his shooting up a Republican baseball field practice a year ago".
At the same time, actor Robert De Niro, one of the intended targets, urged Americans on Friday to get out and vote.
In turn, Mr Trump has called the former USA vice president "Crazy Joe" and "mentally weak".
"No nation can succeed that tolerates violence", Trump told the audience.
You can also see another shot of what appears to be the suspect's van below.