BROWNSVILLE, TEX. — The news here on the border with Mexico travels fast.

Most of it is, in fact, “fake news” — conjecture and unverifiable gossip exchanged over “el Feisbuk,” which is what people here in the Rio Grande Valley call the social network. Instead of snapshots and emojis, it now disseminates warnings. People are frightened, and frightened people repeat things that frighten them more:

Stay at home tomorrow. Immigration and Customs Enforcement is conducting raids in the kitchens.

Don’t send your kids to school on Wednesday. The border patrol is looking for kids with no papers.

Don’t drive down 802 on Fridays anymore.

There’s a checkpoint at the grocery store. They arrested 100 people last night at 10.

Who knows? Some of it might be true.