UVALDE, Texas (NewsNation) — Law enforcement authorities are working to nail down a timeline of the Robb Elementary School massacre in Uvalde, Texas, in which 19 students and two teachers were killed amid witness accounts and reports surrounding the shooting.

Conflicting stories are creating controversy around law enforcement response times and action.

“The desire for the granular details is understandable, but our ability to provide those is really, really, really lacking the first 24-48 hours.” said NewsNation’s Leland Vittert, reporting from Uvalde. “They simply don’t have the minute-by-minute timeline here.”

Authorities are saying the shooter may have been in the school for up to an hour before police could break through the barricaded classroom.

Among the first responders were state troopers, the local sheriff, local police and off-duty and on-duty Border Patrol agents — including Border Patrol tactical teams such as SWAT.

Vittert said it’s important to be “very careful” when hearing reports from parents and we have to wait until official data is released.

Analysis: First responders face chaos, horror at school

It’s important to keep in mind, it is unknown when the video of the parents being upset took place in the timeline. Had the shooter already been killed? Had law enforcement already gone in, only to have to come back out to try and find somebody who could unlock the steel door? 

Schools have increased safety measures over the years to prevent school shootings, try to mitigate them and prevent gunman from moving inside schools. Some schools have installed heavy steels doors that lock automatically. These doors do allow people to barricade themselves inside a classroom. 

“Any parent who’s standing out here and hearing gunshots, knowing their kid’s inside, is going to be screaming at anybody out here to go do something — understandably so,” Vittert said.

The Robb Elementary School campus is big. It is hard to know exactly what is going on inside and on the other side of the school.

The Texas Department of Public Safety has said from the time the gunman drove up in his truck to the time he was shot and killed inside the school, around 40 minutes had passed.

Uvalde is a small town. Vittert suggested that there are only a handful of police officers on duty at a time, and it is still too early in the investigation to make assumptions of the police response timeline.

In the time between the shooter’s arrival and death, a lot of children had been evacuated from the school as well. Police were also met with a locked steel door that barricaded the shooter inside the classroom. They needed to hunt down an employee to help let them inside the classroom.

There was a lot going on at the time of the shooting. Vittert mentioned that one of the local deputies lost his daughter in the shooting: “He arrived at the school to respond to the shooting and found out that his daughter had died.”

An off-duty Border Patrol tactical team heard the call and responded to the incident. One of the patrol agents, who ended up shooting and killing the gunman, was wearing a baseball hat that a bullet went through, just grazing his head.

Vittert analyzed this agent’s response, saying, “The fact that he just had a ball cap on, and didn’t even take time to put on his full tactical gear — his helmet and body armor they typically wear — that speaks to a timeline that is compressed, and it speaks to officers that went in to confront this gunmen without regard for their own lives.”

Vittert suggested these actions by the patrol agents speaks against any kind of “complaint” that they waited too long.