It happened in a matter of minutes Thursday, bullets flew and victims at Umpqua Community College in Oregon had just seconds to realize that a 26-year-old gunman was attacking them.
"Most people freeze," Hector Alvarez told FOX40 Friday. Alvarez has 25-years of law enforcement experience and teaches classes on how to navigate an active shooter situation.
"This is what I tell my son and daughter, move, get out of the way!" Alvarez told a group of young professionals at the Safety Center in Sacramento Friday.
If you can't run, Alvarez says hide, and use everything around you to build a barricade.
In the classroom at the Safety Center, Alvarez encouraged students to barricade themselves in the room by building a fortress of chairs and tables in front of the door.
For more information on classes, go to http://www.workviolenceprevention.com/