An off-duty firefighter detected a dangerous carbon monoxide leak at a restaurant when people started acting strangely at dinner Saturday evening.

"People were starting to act a little weird," Lewisville, North Carolina firefighter Jacob "Lonnie" Wimmer told WGHP. He was at River Ridge Tap House celebrating a friend's 30th birthday. "Heads hurting, People holding their belly and going to the bathroom a lot."

All their symptoms showed signs of carbon monoxide poisoning.

“Some of the adults were acting nauseated, sick,” said Wimmer

He immediately called the fire department, which soon discovered high levels of carbon monoxide in the restaurant.

Wimmer’s swift action helped more than 30 people inside the restaurant. First responders say the situation could have been a lot worse if Wimmer wasn’t there.

As thanks him for his quick thinking, Wimmer walked in Lewisville’s Christmas parade instead of working his typical day shift.