A surfer who went missing at an Australian beach is now believed to have been the victim of a shark attack, according to authorities.

For the fourth time in 20 months, South Australia's surfing community is collectively grieving — this time after a shark attacked a 28-year-old man on the state's west coast.

Just after 7 p.m. local time on Thursday, a 28-year-old man from Port Lincoln, a city on the Eyre Peninsula, was surfing near Granites Beach, south of Streaky Bay, when witnesses reported seeing a shark attack the man, South Australia Police wrote in a press release early Friday.