Tulsa Police Chief Wendell Franklin outlined the process that his department follows once there is an active shooter situation.
He said the activation occurs through the 911 system that alerts every city police officer.
"So when we get that call, we are going to disregard any safety measures that we might have for ourselves and we are going to go in the building to deal with the threat. Our philosophy is we will stop the threat and we will do that by any means necessary," he said.
Law enforcement "performed heroically, in my opinion, and I cannot thank enough the response not only from our locals, but also from the FBI, the United States Marshals Service, the ATF," he added.