Why did Austin airport's fire alarm go off?

AUSTIN (KXAN) — Operations inside the Barbara Jordan Terminal at Austin-Bergstrom International Airport are returning to normal after a falsely-triggered fire alarm caused an evacuation Wednesday morning.
The airport issued an alert about the terminal evacuation on social media around 7:45 a.m., asking passengers to follow directions from staff to exit the facility.
About 15 minutes later, the airport said in an update the alarm was canceled, and passengers were reentering the terminal and