At a high school just outside of Phoenix, a madman stalked the halls. Suddenly, shots rang out and people started screaming.
It was just a training exercise, but the situation is every parent's worst nightmare, which is why controversial Sheriff Joe Arpaio of Maricopa County, Ariz., has called on his all-volunteer sheriff posse -- 3,000 civilians strong -- to keep Maricopa County kids safe.
Today, these men and women, many of whom are retirees, were learning tactics that they might have to use to bring down the next school shooter. Their coach was '90s action film legend Steven Seagal.
"For every second that goes by, I told you this, you are going to have dead children," Seagal told the volunteers.
The "Out For Justice" star knows a thing or two about simulated shootings, but in this case he was not acting. He, too, was a full-fledged member of Arpaio's official posse.
The sheriff's big idea is to have his posse members patrol the county schools. Of the 3,000 posse men and women, 500 were certified to be armed. They can wear sheriff uniforms and drive marked cars, and it is all perfectly legal. In fact, several states have civilians in official sheriff posses conducting patrols.
The posse school patrol was only the latest high-profile gambit for the man they call "Sheriff Joe," but now the stakes are higher than ever.
Five minutes is all it took for the horror to unfold at Sandy Hook Elementary School in Newtown, Conn. But since the massacre of 20 children at Sandy Hook, there have been other school shootings in California, Georgia and Texas, just to name a few.
So now the great debate is joined: How can we protect our children?
This week, the National Rifle Association offered one answer: Arm teachers.
But in Arizona, Sheriff Joe has decided to take matters into his own hands with his school patrol posse.
"If we have to take action, we will take action," he told "Nightline." "We will go on the school grounds, and we will go into the schools if there is some type of catastrophe that's going to happen."
If you haven't heard of Sheriff Joe, well, that is almost hard to believe.
Since he was elected sheriff of Maricopa County in 1992, Arpaio has been a publicity machine -- on immigration, prisoners' rights, gun control, you name it, this man has found a way into the national discussion. Now he has an angle on school safety, even appearing in promo clip during an NRA news special, but he said he is not out to do the NRA's bidding.
"This is one sheriff who is a lone ranger," Arpaio said. "I don't copy other people, what they do. I think my 20-year history shows that. So if you think I copied people? They copy me. I'm not trying to brag."
The school posse will patrol near schools in the mostly rural, unincorporated towns of Maricopa County.
Some people in different parts of the country might hear the word "posse" and think it is an undisciplined gang going around helter-skelter without proper police supervision, and potentially endangering the community, but Arpaio said he doesn't see it that way.
"Maybe [those people] are watching too many old cowboy movies, but the concept is the same," he said. "Instead of going after horse thieves, we go after car thieves and anybody else that violates the law."
Mike Garstat is one of Sheriff Joe's possemen -- one of the 500 volunteers who are certified to carry a weapon -- and the gig is not glamorous. They spend their time roaming around different school grounds on the lookout for any sign of trouble.
"It's pretty random and sometimes pretty monotonous," Garstat said.
A 38-year-old father of three, Garstat works as a radar technician at a nearby airport. He said volunteering for Arpaio's posse is like a hobby for him.
"It gives me the ability to keep my community safe, to keep my kids safe," he said. "Some people take up pottery. Some people take up poker playing. I choose to do this."
Garstat and the other volunteers never actually enter school grounds. They just patrol the surrounding areas, which include strip malls, parking lots and apartment complexes, looking for that dangerous needle in a haystack.
"All of these businesses and communities are interconnected," Garstat said. "The school patrol is essentially a community patrol."
But some gun control advocates said armed civilians patrolling anywhere near a school could be a recipe for disaster. Some of the parents who spoke to "Nightline" at a school on the posse's watch agreed.
"You have people that have weapons on them, that can murder other people, and they are volunteers," said Donna Wetzel, whose son attends Paradise Honors High School. "They are not police officers, they are not military folks and, maybe, they may not like the look of a kid walking down the street. And I worry about instances like what happened in Florida with Treyvon Martin."
While some critics of Arpaio's program have said the posse volunteers are "rent-a-cop" amateurs who could be potentially risking kids' lives, Arpaio stood by his posse.
"I've been doing this for 20 years. Nobody complained," he said. "I used the posse to go after illegal immigrants, dope peddlers, everything else."
Arpaio added that the volunteers receive law enforcement training, but when asked if it was the same training they would get at a police academy, the sheriff said, "not exactly."
"They don't go through that many hours, but they have preliminary training" Arpaio said. "You can go through all the training you want, but it's the common sense that makes a difference."
Arpaio has built his posse over the years and assigned them all sorts of tasks, including patrolling malls during the holidays, investigating President Obama's birth certificate and hunting down undocumented immigrants.
The Obama administration's Justice Department filed a lawsuit, accusing Arpaio of "a pattern of unlawful discrimination."
Activists called it a "reign of terror," and worried that Arpaio's school posse will be part of it, feeding on the pressure from an anti-immigration sheriff.
But Arpaio called their claims "ridiculous."
"We're not out there to check kids or papers of the parents," he said.
Everybody in Maricopa County seems to know Sheriff Joe. One Hispanic mother who pulled up alongside us as "Nightline" rode along with him thanked him for jailing and straightening out her wayward sons.
At 80 years old, Arpaio still likes all the attention he gets. But is his school patrol posse just PR, or a real solution? Perhaps it's both.
"I want this publicity because I want everybody to know we're out there, our armed posse, the same automobile markings as my regular deputies, same uniforms, same everything," Arpaio said. "So if you want to call me a publicity hound, good."