PERTH, Australia (AP) — Police say a man has been killed by a shark while diving with his brother off a beach in southwest Australia. It's the fourth fatal shark attack in Australia since September, all of them off the continent's southwest corner.

Police spokeswoman Sgt. Naomi Smith says the two men were diving from a boat off Stratham Beach, about 140 miles (230 kilometers) south of Perth, the Western Australia state capital, when one of brothers was attacked midmorning.

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, says an airplane and two government boats are searching for the shark.