On Friday evening, Marina Costello was walking along the beach in Wellfleet, Massachusetts, when she heard the cries. Then she burst into tears herself.

A 300-pound dolphin was lying on its side along the shore, barely touched by the waves.

“I jumped in the water, crying, because I heard it suffering. It’s giving out little noises, and I didn’t expect to hear that, and that just tore me apart," said Costello, 54, who watched it draw its last breath. "After it passed, I was just heartbroken, to see such a magnificent, majestic animal die, it was a tragedy happening.”

The week after the largest mass dolphin stranding event Cape Cod has seen in decades, if ever, the Wellfleet community is "buzzing" with a desire for answers ‒ to try to alleviate their heartbreak and prevent another tragedy, Costello told USA TODAY.

The International Fund for Animal Welfare is investigating the stranding event and performing necropsies ‒ animal autopsies ‒ on the 10 dolphins that died, but locals are worried about more dolphins deaths in the future.

“To say this just happens, well it doesn’t happen," said Costello, who manages the front desk at a local resort. "You don’t see this on Cape Cod just happening like this, it doesn’t happen.”

Even though Cape Cod is a global hot-spot for dolphin strandings, which is when the animals get stuck in too-shallow waters, Friday's stranding of 125 animals is unprecedented, according to locals and wildlife experts.

By Tuesday, federal officials were trying to determine whether Wellfleet's June 28 event was the largest single stranding in U.S. history, the International Fund for Animal Welfare told USA TODAY.

"There's a strong chance this might be one of the largest ever," said Brian Sharp, marine mammal rescue team director at the International Fund for Animal Welfare, a Cape Cod-based rescue non-profit.

Volunteers 'so outnumbered' by dolphins

Going forward, more needs to be done to prevent large numbers of dolphins from getting stranded along Cape Cod Bay near Wellfleet, said Katie Carrier, an administrative assistant at a country club along a beach where dozens of dolphins were stranded Friday.

By that afternoon, she said, everyone was rushing to try to help somehow and filled with anxiety for the dolphins, which can breathe air but aren't able to survive for long outside the water in direct sunlight.

"Everybody was so concerned about the tide that was still coming in, but not soon enough," Carrier, 27, said. "People were driving by, trying to help somehow."

In mass stranding events, people who have not been trained in sea animal rescue should not approach or touch dolphins, wildlife officials warn. The National Oceanic and Atmospheric Administration says marine mammals and sea turtles can behave unpredictably, and people should keep a safe distance from wildlife when calling stranding hotlines.

"We know these animals can suffer irreparable harm by being pulled by their tail," Sharp said, explaining the human equivalent would be being pulled by your foot along a parking lot. "It can cause damage to their spinal column. These animals are made to go forward through the water, not backwards across sand, with their body weight," he said.

If someone sees a stranded dolphin, the best thing to do is call a local stranding responder or 911, Sharp said. Shooing away gulls is also good, because the birds are known to eat stranded dolphins alive.

In Cape Cod, the June 28 mass stranding interrupted a 160-person outdoor wedding held on the beach in the afternoon, Carrier said, as well as a children's summer camp held at the Chequessett Yacht & Country Club.

"We need to be more proactive, so we're not so reactive," Carrier said, adding that the community should consider investing in equipment to provide aerial views of dolphin pods in the bay, so they can get advance warning of potential strandings.

On Friday, approximately 125 dolphins were stranded, spread out over a mile, according to Brian Sharp, marine mammal rescue team director at the International Fund for Animal Welfare.

Only about 80 IFAW staff and trained volunteer rescuers were available on the beach Friday, Sharp said. Some IFAW staffers are still recovering from cuts, bruises and sore muscles they got herding dozens of dolphins on foot, in dangerously thick mud, over the course of five days, Sharp said.

“We were so outnumbered," he told USA TODAY.

Sharp said even more year-round rescuers are needed, especially between December and April, which is historically when the most strandings typically happen, he said.

After conducting marine rescues for the past 26 years in Florida and Massachusetts, Sharp said Friday's mass stranding was "by far the largest event" he's seen.

Rosalie Puffer, a manager at a local seafood restaurant, was born and raised in Wellfleet, and said the number of dolphins stranded Friday was shocking.

"The community is used to these types of things happening, but the vast number of the stranding was pretty intense for everyone," Puffer, 31, said. "I've never heard of that number," she said.

Wellfleet community is heartbroken, kids are shaken

Wellfleet, is a "hot-spot within a hot-spot" for dolphin strandings in Cape Cod Bay, Sharp said. The town, located halfway between the tip and the "elbow" of Cape Cod, has a year-round population of about 3,000, which increases as much as six-fold during the summer months.

The gently sloping sand and mud flats cause the tide to "drop out" quickly, Sharp said, and the area where the dolphins got stuck in too-shallow waters Friday is a particularly dangerous, maze-like trap for dolphins and boaters.

Fishermen in the area told IFAW rescuers Friday that there was "a lot of bait fish," Sharp said, adding, "as we were herding the animals out we saw some bait fish."

Warmer ocean temperatures have caused dolphins' prey to move into different areas, and when one dolphin in a group, or pod, goes searching for food, others follow. That could have been what happened Friday, Sharp said.

“This could have been just a simple large group of dolphins that came into the area trying to find food, but it’s an incredibly dangerous area because the tides drop out," he said.

Puffer, a manager at Mac's Shack seafood restaurant said people who are concerned about the dolphins should donate to rescue efforts, that way more teams can be funded.

Carrier, the country club assistant, said maybe something should be done to divert dolphins away from Cape Cod Bay, to prevent more dolphin deaths.

“The most important thing is, we just want to know what caused this, so that it can be prevented from happening again," said Costello, the resort clerk.

Diverting tactics worked during the cape's last massive stranding event in 2012, Sharp said, in which underwater microphones were used to locate dolphins and get them headed back in the right direction before they got stranded. During the 2012 event, about 60 dolphins were stranded over about three months, according to IFAW.

On Friday, shaken locals who had witnessed the stranded dolphins gathered at local seafood restaurants to console one another, including children who had questions about whether the dolphins would be okay, Carrier said.

"It stressed them out. They understand there's something going on in the area, and then you have to answer all those questions, and how should you address them?" she said, adding that she's grateful her 2-year-old and 4-year-old daughters didn't see the dolphins.

Puffer, who has six young nieces, said she thinks parents can turn conversations about the stranded dolphins into an opportunity to educate kids about the importance of wildlife rescue teams, and how humans can track dolphins in the ocean to make sure they're okay.

"Hopefully this does turn into a spark that will rally people together to help volunteer or donate, or make everyone more aware of why this is happening," Puffer said. "Instead of dividing people, hopefully it brings people together."