AVENTURA, Fla. — One sticker has a Photoshopped image of President Trump standing on a tank, haloed by fireworks with an American flag behind him. “Dishonest Media,” and “CNN Sucks,” reads another one, the cable network’s logo affixed to it. And then there are the memes expressing support for the president and animosity toward his critics.

A white van plastered with these and other bombastic stickers was seized from a South Florida shopping center on Friday morning, in connection with Cesar A. Sayoc Jr., a man the federal authorities have charged with mailing a string of packaged bombs to a range of high-profile Democrats.

Photographs of the van, believed to be Mr. Sayoc’s mode of transportation and his home, is a kind of Facebook feed on wheels: Many of the decals appear to show widely-circulated conspiratorial internet memes that Mr. Sayoc himself posted in repetitive bursts on his social media accounts.

“He communicates in meme,” said Jonathan Albright, a researcher at the Tow Center for Digital Journalism at Columbia University who was analyzing Mr. Sayoc’s social media accounts on Friday. “The van is basically his identity, in meme.”