In a series of sheds on the edge of a Texas airfield sits the training centre that has set the national standard for how American police deal with active gunmen.
It is barely a hundred miles from Uvalde, where 19 students and two teachers were shot dead at their school on Tuesday.
The admission by police that they got it wrong as the shooting was unfolding, that they should have confronted the gunman earlier, has raised the spectre that lives could have been saved.
Police in Uvalde say they were properly trained but it is clear something went catastrophically wrong as the minutes ticked by with gunman Salvador Ramos inside the school.
The Advanced Law Enforcement Rapid Response Training (ALERRT) centre near San Marcos in Texas has trained 130,000 law enforcement and fire officials nationwide in "dynamic force-on-force scenario-based" courses. It is the FBI's training of choice.
They watched the events in Uvalde with horror and believe failings in the police response were exposed.
Assistant director John Curnutt said: "I understand why it was difficult that they were put into the situation they were put into, but I understand that we know enough about these incidents that we should be training for stuff like this."
A veteran of 18 years in SWAT teams, Mr Curnutt has been in that situation himself.
"The plan A doesn't work? What's the plan B, C, D? We have to have these capabilities, it's required of us.
"Winston Churchill once said: 'Sometimes doing your best isn't good enough. Sometimes you must do what is required'."
In Uvalde on Tuesday, he said, law enforcement showed failings in leadership, equipment, mindset and applying the training they would have undergone.
"Every single one of these events is a watershed moment for us. Every single one of these breaks our heart and chews up our soul just a little bit each time.
"We want to make sure that, if we can't prevent them, we're darn sure going to respond to them to the best of our ability."
It is a sad reality of American life that, for years, schools have been required to conduct active shooter drills, teaching the youngest of children how to deal with the most awful of situations.
Staff at the ALERRT centre ran through an exercise on how to confront a gunman in a mock classroom.
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It was chilling to be in that room as he shouted threats and fired blank rounds from an assault weapon before being taken down by responding officers.
Everyone there recognised it is easier to get things right in a training scenario, much harder to do so facing automatic fire in the heat of battle.
But Mr Curnutt said, whatever the risks, that is the job.
"Those kids deserved better. Those kids deserved everything we could throw at it."