The mock protesters are harmlessly dispersed with a high-tech device. 

It is called the Active Denial System. Using an electromagnetic beam that travels hundreds of meters, it heats people’s skin enough to trigger their instincts to flee. 

In development for over a decade, the device is not new. But it remains shrouded in mystery. 

Colonel Tracy Tafolla heads the U.S. Marines’ Joint Non-Lethal Weapons Directorate.

“Unlike conventional munitions or conventional weapons where you can hold the munition, there’s a bang, there’s something to see," said Colonel Tafolla. "That’s not true here. You can’t see it, you can’t hear it. You can’t smell it.”

Developers say 11,000 tests show it is safe, with no known lasting effects. It causes a quick sensation of a hot blast - like opening the door of a hot oven. 

Officials in Los Angeles considered a smaller device two years ago, as a way to break up jail fights. Bob Osborne, a commander at the Los Angeles County Sheriff’s Department, says it was never used.

“I don’t know if it was because of public pressure, or something with the Department of Justice, we were never privy as to why the program was stopped," said Osborne.

Four years after it was introduced, the military has not used it either. 

Researchers say fear of the unknown is a big factor. Stephanie Miller is one of its developers and has tested it on herself many times.

"Understanding it very well, I say it’s not exotic, but people who don’t understand about it feel that it’s kind of mysterious. I think we’ve not embraced it because it’s new," said Miller.

Recent riots in Afghanistan have brought the device to the forefront again. 

Joseph Trevithick is a defense analyst. 

Especially with the recent Quran burning incident we see the need for dispersing crowds outside of U.S. facilities or facilities where U.S. personnel are operating," he said. "These kinds of non-lethal systems provide that capability."

By inviting journalists to watch, the military hopes to remove any mystery surrounding the Active Denial System. 

“Is there an apprehension of employing this kind of technology? I would say probably. It’s something that’s not well understood," said Colonel Tafolla.

With millions of dollars spent on developing the technology and budget cuts expected soon, the pressure is on for U.S. forces to use the gun or perhaps end the program.