The deadly shooting in Las Vegas is changing the way some local businesses train their employees. Several 911 dispatchers from across Tennessee took part in a training class in Knoxville this week.

The class was organized by APCO international. Officials say APCO is the largest public safety education organization in the world.     

"No one thinks it's going to happen in their town or in their city, but I think now people are realizing that it can indeed happen anywhere," said APCO instructor Tracy Ertl. 

Tracy Ertl is a Communications Supervisor at a 911 emergency center in Green Bay, Wisconsin. She also teaches active shooter classes nationwide. 

" I teach this class because I was in Omaha Nebraska when their active shooter incident broke out at the Westroads mall," said Ertl.  

Her class teaches 911 dispatches and first responders what they can expect in the heat of the moment. 

" Active shooter and active assailant calls, they come out of nowhere," said Ertl. " You'll get the call of a person down or maybe it will come in as a medical call and very quickly you'll realize that it's an active shooter or active assailant call. It's going to be a multitude of calls, it's not going to be a regular or every day or every night business. It's going to be an onslaught of calls and so the way we normally operate is going to have to go out the window." 

The class also teaches dispatchers how to prioritize calls during a mass casualty event. When dozens of calls come in, time is everything.

 " The public needs to be prepared for us not to be able to stay on the phone to comfort them during an active shooter incident," said Ertl. "We're going to ask information about the shooter or shooters and we're trying to fire out where they are." 

She says it's important to move on to the next call quickly, because that caller may have key information to help police find or stop an active shooter. Ertl says no piece of information is too small. 

"Call if they have information, even if it's just part information," said Ertl. " Whatever they have, it could make a difference between life or death." 

Ertl also uses surveillance video to help show civilians what suspicious behavior looks like. The video shows many people freeze or wait to verify a shooting with their own eyes, before reacting. 

 " We need people to act on first instinct, your gut instinct will almost never lead you wrong," said Ertl. " If it looks like it, if it sounds like it probably is it." 

Most importantly, Ertl encourages every family to have a conversation and a plan of action. 

" It's not just schools anymore, in fact the largest number of active shooter incidents are taking place in public places and in work places. We can't ignore that the threat is here and unfortunately it's here to stay," said Ertl. " What we're teaching is quickly evolving so there is so much information, but we need to talk to our friends and family and be prepared."