Southwest passengers experienced quite the scare on Tuesday. While on board flight 3426 in route to Tampa, Fla, the pilot declared "we're going down" over the intercom system.

Shelley Wills, one of the passengers on the Boeing 737 told ABC's affiliate there. "And everyone is looking around like, 'Is this a joke? Is he serious?' And then you felt the nosedive."

"At first it sounded like someone was coming over the PA to talk," Grace Stroud, another passenger, told CNN. "Then it sounded like shots through the cabin, twice, back to back. Seconds later, the panicked captain said, 'We're in trouble, we're going down.'"

In a statement, Southwest said "Flight 3426 experienced a maintenance alert as they were on descent into RDU...The captain declared an emergency and descended the aircraft to 25,000 feet where the alert was resolved. Throughout the remainder of the descent the flight was normal, landed uneventfully, and was not met by emergency vehicles."

The FAA said it is investigating. 

Read more: KTRH