(CNN) -- A popular Western Australian beach was closed to the public Monday as authorities hunted for the shark they believe killed a 21-year-old man while he was out boogie boarding with friends.
Dunsborough Police Sgt. Craig Anderson said the man, who was not identified, was boogie boarding in a tourist haven known as Bunker Bay when a shark apparently bit into him. His friends, as well as a fellow surfer, were able to drag his body -- which had "significant injuries" in its lower half -- onto the beach, where rescue personnel soon arrived.
But Anderson said that authorities now believe the man died while he was in the water.
"When we share the water with aquatic creatures, these things will happen from time to time," said Anderson, adding that the man's death has shaken residents in the picturesque southwestern Australian coastal community. "It is all a bit quiet today in town."
James Cottrell told CNN affiliate Channel 10 that the victim had phoned him Sunday morning, saying he "was pretty keen to surf."
"I just didn't believe it," Cottrell said of his friend's death. "It's too much to comprehend, really."
A 31-year-old man died just over a year ago while surfing about 45 kilometers (27 miles) away from this weekend's incident, in Cowaramup Bay. But this is the first shark attack, in Anderson's recollection, to happen in Bunker Bay.
Yet the police officer admitted that conditions may have factored into the shark being in the vicinity.
For one, a seal colony -- common targets for sharks -- sits west of where the incident occurred, part of a wealth of sea life that makes the bay "quite active."
Moreover, there were fairly overcast skies over a "dark and gloomy" sea, at the time.
"It was just ideal shark conditions," Anderson said, alluding to his conversations with local experts. "Unfortunately, everything stacked up."
That said, no one -- including the victim's friends and nearby surfers -- reported that they saw the shark at the scene. Nor have there been any sightings, beyond unconfirmed reports from canoeists, in the general area.
The beach has been closed to swimmers and surfers for a 36-hour period until at least midnight Monday, Anderson noted.
In that time, aircraft from a government fisheries department will conduct "a sweep of the bay and the coastline looking over areas where the shark may be lurking."
Several rescue boats were in the area as well, searching closer to the water's surface.
Later Monday, the heads of several local government agencies will convene to discuss what to do next. That could include possibly reopening the beach Tuesday morning even if one or more sharks aren't spotted, which Anderson said is possible.
"It's their habitat out there," he said. "They can be very elusive creatures."