The scene was a part a school drill that aims to prepare students and staff members for the worst case scenario.
The lockdown drill had all the trimmings of a frightening school shooting -- doors chained shut, a shooter on the loose.
The phony gunman fired into hallways as teachers followed protocol by locking doors, closing blinds, gathering kids in corners and emailing head counts.
"When police get here, they need to know who's missing and who's accounted for, and that's a big task in a school this size," said principal Rob Morrow.
Police and SWAT team members stormed the school. Half a dozen agencies treated this mockdown like the real deal, using the practice to hone their tactics. After observing, dispatchers figured how to better field calls from frantic parents while tackling other 911 emergencies.
"We have calls receivers assigned - this is just my idea - to field just parent calls," said Debi Nelson, communications center supervisor.
Even after six years of drills, she watched a wounded teacher dial 911 during the drill on Wednesday,Nelson had never thought to ask: "Is your door locked? How are we going to get to them? Need to let deputies and aids know have an injured person in the classroom, but the doors locked."
Communication between agencies is crucial.
"If you go back historically and look at any shooter that's been in a school or mall, the communication breakdown is where thing fall apart," said Aaron Tyerman, medical services operator.
First responders say it's improved but not perfect. Until police secure a safe zone, medics can't treat victims.
"I thought maybe the safe area wasn't quite safe when we first started to bring fire into the parking lot, because of so many second-story windows, we'll talk about that," said Sam Shirley, Tahoma school resource officer.
Lessons learned today are ones they hope they'll never have to use.