PLANTATION, Fla. (Reuters) – The man suspected of mailing at least 14 pipe bombs to some of US President Donald Trump’s leading critics was arrested on Friday in Florida on federal charges in a case echoing the rancor of one of the most toxic election campaigns in decades.

Cesar Sayoc, 56, a part-time pizza deliveryman, grocery worker and former stripper once charged with threatening to bomb an electric company in a billing dispute, was taken into custody by federal agents outside an auto parts store in Plantation, Florida, near Miami as helicopters flew overhead.

Authorities also seized a white van that Sayoc appeared to have used as his dwelling, its windows plastered with pro-Trump stickers, the slogan “CNN SUCKS” and images of Democratic leaders with red cross-hairs over their faces.

Fingerprint and DNA evidence helped identify the suspect, but his arrest did not necessarily end the threat, Federal Bureau of Investigation Director Christopher Wray warned at a news conference.

“There may be other packages in transit now and other packages on the way,” Wray said.

One federal law enforcement source told Reuters that authorities were investigating whether other individuals were involved and did not rule out further arrests.

Sayoc’s arrest followed an intense four-day manhunt sparked by the discovery of bombs concealed in packages addressed to such leading Democratic figures as former US President Barack Obama and former first lady and Secretary of State Hillary Clinton, whom Trump defeated in the 2016 presidential race.

Some of the parcels also contained photographs of the intended recipients marked with a red X, according to a criminal complaint in Manhattan federal court.

The complaint accused Sayoc of sending 13 bombs to 11 individuals, starting with billionaire Democratic donor George Soros. A package surfaced on Monday near his home in Katonah, New York.

A 14th package was found on Friday at a post office outside San Francisco addressed to another wealthy contributor to the Democratic Party and liberal causes, Tom Steyer.

The bombs were sent in manila envelopes lined with bubble wrap and consisted of plastic 6-inch pipes packed with explosive material and wired to small clocks and batteries, the complaint said.

Wray said investigators had yet to determine whether the bombs were actually “functional,” but added that the devices could be dangerous “if subjected to the right combination of heat or shock or friction.”

All were sent through the US Postal Service system and intercepted before reaching their intended targets without exploding. No one has been hurt.

But the bombs have heightened tensions during the closing days of a highly contentious campaign ahead of the Nov. 6 elections in which Democrats are battling to seize control of Congress now held by Trump’s Republican Party.