A traveler at Sky Harbor has uploaded a video of TSA employees performing an "all-stop drill." Passengers had already passed the security checkpoint when agents told them to stop moving. The video uploader, who captured the final 24 seconds of the drill, posted in comments it was unclear what was happening, writing:
"I suddenly found myself in a bunch of travelers who were being sharply told to 'Stay right where you are! Don't move!'

"A TSA employee was pointing his blue-gloved hand at anyone who moved a muscle (including airport workers) and barking these orders. Beyond him were two other agents doing the same thing to everyone in a 90-degree radius. The tension was rather palpable, as you might imagine. No explanation was given, no other words were spoken.

"No one moved a muscle. Parents grabbed their children. Anyone who fidgeted or made a step forward got yelled at."

Nico Melendez, regional spokesman for the TSA, said they use "all-stop drills" to help prepare employees for a security breach.

"They're called in case something happens at the checkpoint where we need to have everyone stop to be able to identify a problem or an issue," Melendez said.

"We seize all operations of screening and we have all passengers stop where they are so we can identify what we need to identify."

Melendez said agents are supposed to tell passengers a drill is underway.

"Usually passengers are given some kind of a warning that there's a drill being conducted and they're thanked for their patience," Melendez said.

The drill is conducted daily at airports across the country, according to Melendez. It usually takes no more than two minutes.

"I've never seen a case where tension was palpable or there was any issue," Melendez said. "I've never seen passengers react in a negative way."

The TSA implemented "all-stop drills" about a decade ago.