OAK ISLAND, N.C. — Beachgoers cautiously returned to the ocean Monday after two young people lost limbs in separate, life-threatening shark attacks in the same town in North Carolina.

A 12-year-old girl lost her left hand and suffered a leg injury Sunday afternoon; then, about an hour later and 2 miles away, a shark bit off the left arm of a 16-year-old boy. Both were about 20 yards offshore, in waist-deep water.

A shark expert says the best response after one of these extremely rare attacks is to temporarily close beaches that lack lifeguards, but local officials said they did their best to warn people, and aren't sure they can force people out of the water.

"We moved very quickly yesterday after the first attack. We were trying to get people on the beach with megaphones and ATVs to warn people to get out of the water," Oak Island City Manager Tim Holloman said at a news conference.

Town employees drove along beaches urging people to get out, but the instructions were voluntary and not mandatory. Holloman said officials are still researching whether they could legally force an evacuation if there were another attack.

Earlier Monday, Mayor Betty Wallace told The Associated Press that information was too spotty after Sunday's first attack to justify immediately clearing the water, but that after the second attack, they did warn swimmers to get out.

Witnesses described a chaotic scene as the attacks disrupted one of the first busy weekends since public schools ended for summer. The victims — a girl from Asheboro and a boy from Colorado Springs, Colorado — were bleeding heavily, and other beachgoers applied makeshift tourniquets.

It was "quite nightmarish," vacationer Steve Bouser told the AP. "I saw someone carry this girl (out of the water), and people were swarming around and trying to help ... It was quite terrible."

Surgeons amputated the girl's left arm below her elbow, and she has tissue damage to her lower left leg. The boy's left arm was amputated below his left shoulder. Both were in good condition Monday at the New Hanover Regional Medical Center in Wilmington. Neither name was released.

Dr. Borden Hooks, the surgeon who operated on both victims, said the boy was awake and talking to doctors on Monday but the girl's family asked that no more updates be provided. He said the boy will be at the hospital for several more days but doesn't need more surgeries.

A surf camp scheduled for this week has been canceled.

"We just thought that was a prudent measure. A lot of inexperienced people out there flailing around is not necessarily a good thing," Holloman said.

There were only 72 unprovoked shark attacks on human around the world in 2014, including 52 in the U.S., according to the International Shark Attack File at the Florida Museum of Natural History. Three of them — all outside the U.S. — were fatal.

Shark researcher George Burgess, who oversees the database, said he's aware of only two other multiple shark attacks on the same beach in one day. "It may be that there are big schools of fish out in the surf zone that are attracting the sharks," he said.

The first emergency call came in about 4:40 p.m., followed by a call about the boy at 5:51 p.m. And just four days earlier, a 13-year-old girl suffered small lacerations on her foot from a shark bite on Ocean Isle Beach, about 15 miles from Oak Island. Both towns are on barrier islands just off the coast.

Most beaches in North Carolina lack lifeguards, and without authorities keeping watch, the best advice is to close the beach temporarily, Burgess said.

"It would be my best judgment to shut down the beach for the day," he said.

Deputies using boats and helicopters to monitor the water after the attacks did see a 7-foot shark between where the incidents happened, Sheriff John Ingram said. Another shark was spotted Monday morning.

But the town's beaches were open Monday, and officials said they can't stop people from swimming.

"There's no way we're going to stop people from going into the water," said Watts. "There's really no way to control that."

People should avoid swimming where people are fishing, stay out of the water if they have bleeding cuts, and avoid swimming in turbulent water or after a storm, Holloman said.

"Oak Island is still a safe place," Holloman said. "This is highly unusual."

Larry James, of Asheville, N.C., has come to Oak Island for 20 years to vacation. He said he and his wife wouldn't let their six-year-old granddaughter, Maggie, go out far.

"We won't be out in the water so far. Ankle deep at the most," he said

Many others were staying out entirely, said Lori Little, of Claremont, N.C., who was vacationing with her husband.

"I would describe the beach as empty as compared to when we were here yesterday," she said. "I don't think people are quite ready to get in the water yet."

Associated Press writers Jack Jones in Columbia, S.C., and Jonathan Drew and Martha Waggoner in Raleigh contributed to this report.