OXFORD TOWNSHIP, Mich. (NewsNation Now) — The shooting at a Michigan high school Tuesday could have been much worse if many students hadn’t instantly put their active shooter training to work.

“The kids in the school showed a lot of poise and grace under very difficult circumstances.” Jim Maxwell, a former FBI agent who teaches active shooter drills, said on “Banfield.“

Oxford High School just had an ALICE lockdown drill Oct. 7.

ALICE is an acronym that stand for Alert, Lockdown, Inform, Counter and Evacuate.

Students can be seen in videos implementing what they learned during the shooting Tuesday.

In one video, students, barricaded inside a classroom, refuse to open the door for a person because they do not believe the person is a police officer.

“We’re not taking that risk right now,” a student says in the video.

Then, they heard the person on the outside of the door saying “bro,” which some students said was a red flag.

“What when you go into lockdown mode, the administrative group, or the teachers who received this training, are told not to open doors until they receive a signal. the all-clear signal, which is predetermined,” Maxwell said. “These students were on their own and they evaluated this correctly and did the right thing.”

We learned Wednesday that the person was an officer, but Oakland County Sheriff Mike Bouchard said the ALICE training likely saved lives in other ways.

“Those practices were used and they save lives,” Bouchard said. “Desks were up turned, doors were barricaded. Doors were actually hit by gunfire and so were barricades, but the doors were safe. So that behavior, that training and those protocols save lives.”

Bouchard said his advice for anyone would be to have “situational awareness” wherever they are.

“You have to go into a place and look to see where the exits are,” Bouchard said.