Federal authorities say a man in Florida has been arrested in connection to the string of suspicious package bombs targeting high-profile public figures in the last week.

The man has been identified as 56-year-old Cesar Sayoc, an Aventura resident with a felony criminal history, who was born in New York.

Read more: Everything we know about suspected mail bomber Cesar Sayoc

Authorities identified Sayoc by a fingerprint he left on one of the bombs addressed to Rep. Maxine Waters, according to the criminal indictment. Sayoc, who had an extensive criminal history, was most recently fingerprinted in 2015, after he was arrested for stealing $58 worth of goods from a WalMart.

In a press conference Friday, FBI Director Chris Wray confirmed that all 13 packages linked to Sayoc contained explosive devices.

Each device consisted of six inches of PVC pipe, a small clock, a batter, some wiring, and “energetic material.” “It’s potential explosive material that gives off heat and energy through a reaction to heat, shock, and friction,” Wray said. “These are not hoax devices.”

Wray said that there may be other packages in transit, and urged the public to remain vigilant.

Cesar is facing up to 58 years in prison, though prosecutors warn more charges may come.

“This is utterly unacceptable,” said Attorney General Jeff Sessions. “Political violence or the threat of violence is antithetical to our vigorous system of self government.”

Asked why Sayoc targeted Democrats, Sessions said, “I don’t know, other than what you can normally expect. That will be determined by the facts as the case moves forwards.”

The arrest followed reports earlier in the day of heavy police activity around an auto parts store in Plantation, Florida, a city in Broward County.

Aerial footage of the scene outside an Auto Zone showed authorities preparing to tow a white van that appears to be plastered with Trump stickers. Investigators from the FBI, NYPD and U.S. Postal Service have since covered the van in a blue tarp.

The news came just hours after authorities said they intercepted two additional packages, one at a mail facility in Opa-Locka, Florida addressed to New Jersey Sen. Cory Booker, and the other at a mail sorting facility in New York City addressed to former national intelligence chief James Clapper.

So far, police have identified 13 packages targeting 11 people.

Read the indictment here: