UVALDE, Texas – The horrific scope of an elementary school shooting that killed 19 children and two teachers was coming into agonizing focus Thursday amid revelations about the attack, including that the gunman barricaded himself in a fourth grade classroom where most victims died.

Some community members outside Robb Elementary School as the drama unfolded had urged police officers to charge in. “Go in there! Go in there!” women shouted at officers soon after the attack began, said Juan Carranza, 24, who saw the scene from outside his house. The officers did not immediately enter the building, he said.

Javier Cazares, whose daughter, Jacklyn, was killed in the attack, said he arrived while police were still outside the building. Upset that they weren’t moving in, he suggested to several other bystanders that they charge into the school.

“Let’s just rush in because the cops aren’t doing anything like they are supposed to,” he said. “More could have been done.”

Most victims reportedly shot in first minutes of carnage

Most if not all of the victims were shot within the first minutes after the gunman arrived at the school, according to the timeline from Texas law enforcement officials obtained by The New York Times. The timeline also indicates that early reports that the gunman initially had exchanged fire with an officer outside the school are incorrect. The Times, which said the timeline was described by a person familiar with the investigation, said the officer was actually in a car nearby and rushed to the scene after the first 911 calls came in.

As the officer arrived at the school, the gunman was already approaching, began firing at the school and entered, according to the Times. Within minutes, other law enforcement officers had arrived and two members of the Uvalde Police Department entered the school. The gunman already had gone inside a pair of adjoining classrooms and was shooting, according to the timeline. The two officers attempted to enter, were shot, and retreated as the shooting continued inside the classroom, according to the Times.