Updated 3:56 p.m. | Justice Department and law enforcement officials announced Friday afternoon that a fingerprint and possible DNA evidence led to the arrest of Cesar Sayoc Jr. in the investigation of package bombs mailed to prominent Democrats.

A “latent fingerprint” on an envelope sent to California Rep. Maxine Waters was key to cracking the case, FBI Director Christopher Wray said. The 13 bombs found so far were not “hoax devices,” he said, calling them “IEDs,” or improvised explosive devices. 

“There may be more to come,” he said at an afternoon press conference, warning that more bombs may be in the mail.

Watch: Sessions, Wray Discuss Suspicious Packages Arrest

Sayoc, a registered Republican, was taken into federal custody Friday and has a lengthy criminal history in Florida dating back to 1991, including drug and fraud charges and felony theft. He has been accused of threatening to use a bomb in the past, according to public records.

The suspect faces five federal charges — including interstate transport of explosive devices, illegal mailing of explosives, threatening former presidents and assaulting federal officers — and up to 58 years in prison. 

Attorney General Jeff Sessions said that, as with any case, the charges may expand or contract. 

He called the explosive devices “utterly unacceptable” and said political violence or threats of violence will not be tolerated. When asked why Sayoc was targeting Democrats, Sessions said, “I don’t know.” 

“He appears to be a partisan, but that will be determined by the facts as the case goes forward,” the attorney general said.

The string of package bombs had set political figures on edge this week. Three packages were recovered Friday: one in Florida addressed to New Jersey Democratic Sen. Cory Booker; one in California sent to Democratic Sen. Kamala Harris; and another in New York addressed to James R. Clapper Jr., the Obama-era director of national intelligence.

Other packages, all mailed in manila envelopes with Forever stamps, were sent to Democratic megadonor George Soros, former Secretary of State Hillary Clinton, former President Barack Obama, former Vice President Joe Biden, former Attorney General Eric H. Holder Jr., former CIA Director John O. Brennan (through CNN), and actor Robert DeNiro.

Many of the bomb targets have clashed with Trump in the past. The president has derided Waters as a “low IQ person” and retweeted conspiracy theories about Soros. At an awards ceremony in June, DeNiro said “F— Trump” during a rant. 

Booker and Harris drew national attention last month during heated confirmation hearings for Trump’s Supreme Court pick, Brett M. Kavanaugh, and both are seen as contenders for the presidency in 2020.

None of the devices exploded before they were recovered by authorities. While the FBI’s lab is still working to determine if the devices were functional, Wray said, they did contain “energetic material” — meaning the right combination of heat, shock or friction could have set them off.

Asked if Sayoc was working alone, the FBI director said, “We do believe we caught the right guy,” before adding that it was an active and ongoing investigation.

President Donald Trump called him before the press conference to congratulate and thank him, Wray said.

While confirming the arrest a few hours earlier, Trump said he was “committed to doing everything in my power as president to stop” politically motivated violent acts.  

“We must never allow political violence to take root in America. We cannot let it happen,” he said. “The bottom line is Americans must unify.”

John T. Bennett contributed to this story.