Robb Elementary School mass-killer Salvador Ramos had terrified teachers before his slaughter — even acting and “dressing like a school shooter” as far back as last year, a special hearing was told.

Fears about the 18-year-old loner’s troubling behavior came up “several times” during interviews after Ramos killed 19 children and their two teachers in Uvalde, Texas, in May, Texas Department of Public Safety Director Steve McCraw told a state Senate hearing Tuesday.

“We had one teacher who said she always was worried about him — he was the one student who scared her most,” McCraw told the hearing while detailing the “abject failure” of the police response.

“Last year he … started dressing like a school shooter, started acting like a school shooter,” he continued of the teacher’s fears.

“He certainly took on the persona of a school shooter in dress and demeanor over the last year, and people noted this.