“They went to where they were supposed to be. But they didn’t go in for action,” said Vincent Salazar, whose granddaughter Layla Salazar died in the shooting. “It’s like it didn’t matter about these children, the way they responded. They were just standing there. That’s what I took from it. This is a horrific thing.”

The video does not contain images of the victims. Still, long stretches of time when officers were standing idle, some of them looking at their phones, were also hard to watch, Mr. Salazar said, particularly one moment when an officer in a helmet and a vest strolled to a hand-sanitizer dispenser.

“What I saw, that idiot putting sanitizer on his hands, it was painful to watch,” he said. “They were not there for their own health. They were supposed to be there to protect the families, to protect the babies.”…

The video did not contain footage of officers confronting and shooting the gunman, nor any images of victims. Yet several family members said the sight of the officers simply standing in the hallway — and early on, falling back — was upsetting in itself.