(NewsNation Now) — Law enforcement and students have credited the school district’s active shooter training with helping those inside the school know what to do when four classmates were killed and seven others were injured at Oxford High School in Pontiac, Michigan.

Students and staff barricaded classrooms and armed themselves with objects, including scissors, in case they needed to fight back.

Daniel Pascal, a security and emergency management professional who works with groups to create emergency plans, said training and preparedness were key to the tragedy not being worse.

“It starts with our school administrators promoting these (safety) programs,” said Pascal. “And our school superintendents and leaders absolutely having resolve and saying they’re committed to providing that training.”

Pascal said he doesn’t have a definitive solution for ending school shootings in the U.S. but believes taking warning signs seriously is a start.

“I would tell you that looking at early warning intervention strategies, and that is ultimately creating a climate and a culture in our schools that is open, and one of community where our students, our staff members, and even parents feel free to communicate the concerns they may have over a student or even another staff member,” said Pascal.

He’s been teaching and advocating school safety for more than 25 years and said the times have evolved.

“Many of us probably remember going through our fire drills. And we didn’t really know exactly why we did them in school, but we did know we were going to get out of class for 20 minutes,” said Pascal. “Well, that’s completely changed. And if I think back a generation or so before myself, and I think back to our parents who were preparing for, potentially, things like the Cold War. We’re not in that situation, but obviously, we have to dedicate significant resources in our school systems toward training, early intervention, mitigation strategies and building positive relationships toward response.”