A woman lost her life and a man was seriously injured on Thursday morning, local time, after being attacked by a shark while swimming at a secluded beach in Crowdy Bay National Park, about 300 kilometers north of Sydney in New South Wales, Australia.

According to police, the woman, estimated to be around 20 years old, died at the scene, while the man, also around the same age, was airlifted to a hospital in Newcastle in critical condition. Emergency services arrived at Kylies Beach early Thursday morning following a call reporting a shark attack.

The victims were tourists from Switzerland, a police spokesperson told CNN.

Authorities praised a bystander for his quick action, as he administered first aid to the injured man before rescuers arrived, which likely saved his life. “The courage of some people in moments like this is truly remarkable,” said Josh Smith, head of the New South Wales Ambulance Service. “Exposing yourself in such a situation is heroic and gave us the time to reach the injured man.”

The beach was immediately closed, and authorities began deploying “smart” traps that attract sharks with baited hooks so they can be tagged and released. Surf Life Saving NSW announced that surrounding beaches will remain closed for 24 hours, with drones monitoring the area.

“This is a tragic incident, and we extend our deepest condolences to the families of the woman and the man involved,” said Steve Pearce, CEO of Surf Life Saving NSW. He also urged beachgoers to avoid entering the water at nearby beaches and to follow lifeguard instructions.