(NewsNation) — Authorities are being met with mounting questions and anger over the amount of time that elapsed before authorities stormed in to take out the gunman responsible for killing 19 children and two adults Tuesday at Robb Elementary in Uvalde, Texas.

One school security expert and former Texas Ranger, however, is defending the town’s response.

“They had a lot of security measures in place,” Brad Oliver said on the Thursday edition of NewsNation’s “On Balance with Leland Vittert.”

In addition to his training as an officer, Oliver is a founding member of the Texas Ranger Recon Team and the co-founder of Cinco Peso Training Group — which offers school employees training on how to deal with active shooters.

“What we’re doing is, we’re training the school faculty, the school staff, to have weapons in the school so that they’re immediate responders, Oliver said.

“You talk about all the officers that were headed to the school — they’re first responders. It took four minutes before they got there. Well, that four minutes — before those officers got there — that’s what we need to be focusing in on. We believe and what we’re doing in over 30 school districts in the state of Texas is arming our teachers,” Oliver continued.

Victor Escalon, who is the regional director at the Texas Department of Public Safety, provided a summary of what happened leading up to the mass school shooting in Uvalde on Thursday during a news conference.

According to Escalon, the gunman crashed and jumped out of a vehicle near the school at 11:28 a.m.. Police calls were made shortly after at 11:30 a.m. and the gunman then entered the building at 11:40 a.m. unobstructed through a door that was apparently unlocked.

“Four minutes later, local police departments, Uvalde Police Department, the Independent School District Police Department are inside. Make an entry,” he said. “They hear gunfire, they take rounds. They move back, get cover. And during that time, they approached where the suspect is at.”

Investigators say it was about “an hour” later that Border Patrol tactical teams arrived and made entry into the classroom.

While the timestamp was not confirmed (the video could have been taken well after the shooter was deceased), video footage has surfaced showing frustrated onlookers urging law enforcement to charge into the Texas elementary school.

Juan Carranza, 24, told the AP he saw the scene from outside of his house across the street from the school. He said he heard women yelling, “Go in there! Go in there!” at officers, but noticed they did not enter the school.”

The Texas Department of Public Safety said around 40 minutes passed from the time the gunman drove up in his truck to the time he was shot and killed inside the school, leaving many questioning not only the Uvalde school district seven-person force, but how the 15,000-person city spends 40 percent of its budget on policing, which includes a nine-person SWAT team.

NewsNation host Leland Vittert spoke to a parent who lost a child during the massacre about the ineffectiveness of the local police, asking whether they were cowardly, unprepared or disorganized. The parent said yes to all the above.

Oliver, while sympathizing with the parent, disagreed.

“That’s his opinion and he’s a grieving father so we’re definitely going to have to cut him … slack,” Oliver began. “But what I deal in is facts. Let’s let the thorough report get done, look at it and objectively look at the facts, not emotion,” he continued.