More questions have arisen about the delayed police response to the active shooter attack at Robb Elementary School in Uvalde, TX, that killed 19 students and two teachers.

According to theSan Antonio News Express, surveillance footage seems to indicate that neither Uvalde Consolidated Independent School District Police Chief Pete Arredondo nor any other officer ever attempted to open the doors where the gunman held two classrooms full of children — and that one of the doors may have been unlocked the whole time.

Surveillance video seems to show that the first time anyone tried to breach the doorway was when they had received the keys, more than an hour after the shooting began, People reports.

Police sources told ABC News that investigators now believe the gunman couldn't have locked the doors to the classroom from the inside. In a June 6 interview with ABC, teacher Arnulfo Reyes, who was wounded in the shooting that killed 11 of his students, said that he had previously complained that the door to classroom 111 did not properly lock from the inside.

According to KSAT-TV, the suspect can be seen on surveillance video opening the door to classroom 111 — the same room that Reyes said had the faulty lock.