The report is likely to raise the intense scrutiny and criticism against law enforcement authorities who decided to wait more than an hour before taking down the gunman who continued to murder elementary school students.
The Austin American-Statesman first reported the revelation on Monday.
Police had initially said that they did not seek to engage with the gunman because they thought they had gone from an active shooting to a barricade situation and they didn't want to risk police officers being killed.
That they had at least one ballistic shield early on undermines that defense.
According to KVUE-TV, investigators put together a more detailed timeline of events that showed some officers were growing impatient with waiting outside the room.
"If there's kids in there, we need to go in there," said one officer at 11:52 a.m., about 19 minutes after the gunman entered the school.
“Whoever is in charge will determine that,” responded another officer.
Critics were shocked to find out that children inside the room were calling 911 and begging for help even as police waited outside. There is some evidence that some of those children were shot and killed while police waited.
The last report to enflame sentiment against the law enforcement response involved an interview with Pete Arredondo, the chief of police for the Uvalde school district. Arredondo defended the police response but admitted that he was unaware that he was in charge because he had purposely abandoned his radios when entering the scene of the crime.
Arredondo said he didn't know about the 911 calls from inside the barricaded room because he had no radios to communicate with other officers.
Here's more about the new information from Uvalde:
Uvalde surveillance image shows officers arrived with rifles within minutes | KVUE www.youtube.com