OAK ISLAND, N.C. >> Local authorities defended their response Monday after two young people lost limbs in separate, life-threatening shark attacks in the same beach town in North Carolina.

A 12-year-old girl from Asheboro lost part of her arm and suffered a leg injury, and a 16-year-old boy from Colorado lost his left arm about an hour later and 2 miles away late Sunday afternoon.

Both had been bathing about 20 yards offshore, in waist-deep water. Authorities said they don’t know whether the same shark was responsible.

“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 announcing the attacks and urging people to get out and stay out of the water, but the instructions were voluntary and not mandatory. Holloman said officials are still researching whether they could legally force an evacuation in the event of a future shark attack.

The sheriff’s department also got a helicopter in the air and a boat just offshore, “so I think we were active as quickly as possible,” Holloman said.

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 frightening and chaotic scene as the attacks disrupted one of the first busy weekends since public schools let out for the summer. The girl was bleeding heavily, and other beachgoers applied makeshift tourniquets while asking her questions to try to keep her conscious.

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, said hospital spokeswoman Martha Harlan. Neither name was released.

Both survived because bystanders helped stanch their bleeding and emergency personnel worked quickly to stabilize and airlift them to the hospital 25 miles away, said Brunswick County Emergency Services director Brian Watts.

“Without that, we would have had a different outcome,” he said.

Holloman said a friend of the boy applied a tourniquet. He said Monday afternoon that the boy was from Colorado Springs, correcting earlier information that he was from North Carolina.

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,” he said.

Unprovoked shark attacks on humans are extremely rare. There were 72 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.

The first emergency call came in about 4:40 p.m., followed by a call about the boy at 5:51 p.m., local officials said. 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.

Investigators said they didn’t know whether the same shark attacked both of Sunday’s victims, nor the size of the shark in either attack.

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.

Holloman said Oak Island is working with local law enforcement and the Shark Research Institute to locate that shark, but he wouldn’t say what would happen if they find it.

The town’s beaches were open Monday, and officials said they can’t stop people from swimming. North Carolina faced dangerously hot temperatures of 100 degrees or more, with a heat index showing it felt as hot as 107 degrees on the shore.

“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.”

Holloman encouraged swimmers to avoid people who are fishing, stay out of the water if they have bleeding cuts and not to swim in murky waters, or after a storm.

“Oak Island is still a safe place,” Holloman said. “We’re monitoring the situation. This is highly unusual.”

Many people were staying out of the water on Monday, said Lori Little, of Claremont, N.C., who was vacationing with her husband.

“I would describe the beach as empty as compared to as when we were here yesterday. There were a lot of people here yesterday. In the water, in and out of the water. I have not seen that today at all.”

“I don’t think people are quite ready to get in the water yet,” she added.

Larry James, of Asheville, N.C., has come to Oak Island for 20 years to vacation. He was on the beach with his six-year-old granddaughter, Maggie, and his wife.

“Right now, we’re going to be a lot more careful, that’s for sure. We won’t be out in the water so far. Ankle deep at the most.”

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