UVALDE, Tex. — Journalists had been threatened with arrest for getting too close to the mourners, so Houston Chronicle reporter Julian Gill stayed in the designated media area when he reported on funerals the week after the massacre at Robb Elementary School.

Nevertheless, a phalanx of uniformed bikers confronted Gill outside the cemetery gates. They called themselves “Guardians of the Children” and claimed to be working with police officers who stood watch.