Florida law mandates that every school district have an emergency plan in place in case the unthinkable happens.

And then it did.

Just after 2:20 p.m. on Wednesday, Nikolas Cruz walked into his former high school in Parkland, Fla. In just over three minutes, he shot and killed 17 people, injured 15, and permanently altered the lives of hundreds of students and families.

In the United States, what Cruz did is not unique. For parents and students across the country, the growing frequency of school shootings is making the possibility of a similar atrocity happening in their community feel far too conceivable.  

Paul Parlon is the founder of Parlon Protective Services, a private security company that offers event coverage, security assessments and armored escorts. More recently, the company has been offering training for companies and schools so they can prepare for a situation similar to Parkland, or San Bernardino, or Newtown, or Columbine.

Parlon, a former police officer, teaches school administrators and office managers to implement a predetermined set of reactions to an active shooter situation. Relying on a system, Parlon says, provides some order to a chaotic situation.

"To give the mind less things to choose from allows your mind to clear and react quicker," Parlon said.

 As these situations become more common, the response plan has evolved from a "Run, Hide, Fight" plan to "Move, Escape, and Attack." 

Parlon explained that this newer model promotes a less defensive and passive approach for a more proactive and aggressive mentality. Much of his program focuses on shaping people's expectations during an active shooter situation and what they should expect in terms of a police response. Imagining the situation allows people to put their training into practice, Parlon says.

"This is the right time to start," he said. "This is something that schools state and local businesses should really be thinking about on a regular basis."