"The STEM school doesn't have a school resource officer, but it did have a private security guard, Spurlock said.
And that guard was among the first to confront one of the suspects, said Grant Whitus, chief operating officer of BOSS High Level Protection.
Whitus -- the first SWAT officer to enter Columbine 20 years ago -- declined to identify the guard but said he was "instrumental" in stopping the attack.
He said the guard drew his gun, took the suspect into custody and turned the suspect over to sheriff's deputies.
Had the guard not been on site, "countless lives would have been lost," Whitus said.
But the guard still feels bad that he couldn't stop the entire attack.
"He's a very good guy," Whitus said. "He's wishing he could have done more."

https://www.cnn.com/2019/05/08/us/de...day/index.html