The “stand down” part has been confirmed. The “trucks of militia” part has not. The contractor was repeating something somebody heard that somebody maybe said. It could be a rumor. The threats are real—But “truckloads of militia” so far are not.

Yeah, this is confirmation of wild rumors about "heavily armed militia hunting FEMA, that the national guard encountered but did nothing about", and the national guard pointedly did not confirm those rumors when asked.