A man was killed by a shark on Saturday while diving with his brother off a beach in southwestern Australia, authorities said. It's the fourth fatal shark attack in Australia since September, all of them off the continent's southwest corner.
The two men were diving from a boat off Stratham Beach, about 140 miles south of Perth, the Western Australia state capital, when one of brothers was attacked midmorning, state police spokeswoman Sgt. Naomi Smith said.
She said the diver was apparently killed instantly. His brother was unharmed.
Police have not revealed the victim's name, age, or where he was from.
The Fisheries Department has launched an investigation, which will include an examination of bite marks on the victim's body to determine the shark species.
Tina Thorne, of the department's shark response unit, said an airplane and two government boats were searching for the shark.
She said while police had initially reported that the attack had happened 200 metres from the beach, authorities later calculated that it had happened about a mile from shore.
Experts have been unable to explain the spate of attacks in Australia's southwest, but agree that different sharks are likely responsible for each fatality.
The last fatal attack in Australia was American George Thomas Wainwright, 32, who was taken on October 22 by a 10-foot great white while diving solo off a boat near Rottnest Island, 11 miles west of Perth.
A great white of the same size is believed to have taken 64-year-old Australian swimmer Bryn Martin off Perth's premier Cottesloe Beach on Oct. 10.
The attacks followed the September 4 death of bodyboarder Kyle Burden, 21, who was killed by a shark described as 15 feet long at a beach south of Perth. Witnesses were unsure of the type of shark.
Australia averages little more than one fatal attack a year along an expansive 22,000-mile coast, although attacks have become more common in recent decades as more people take part in ocean recreation.