The 4th of July holiday turned into a nightmare for beachgoers in the waters around South Padre Island, Texas, after authorities said a shark bit at least two swimmers. 

The Texas Parks and Wildlife Department reported that two people were bitten by what is believed to be the same shark, and another two people encountered the shark but were not seriously hurt. Two victims were taken to Valley Regional Medical Center in Brownsville, Texas, one of whom was later airlifted to another hospital, the agency said. Their conditions were not confirmed, and their names were not released. 

In a separate audio statement Thursday evening, South Padre Island Fire Chief Jim Pigg said that three of the victims were hospitalized and the fourth was treated at the scene for minor injuries.

Pigg also disclosed that the shark "was located at the south end of the island and was pushed out to deeper water."  

At around 11 a.m. local time Thursday, officers responded to a report of a man who had sustained a severe shark bite near the 4100 block of Gulf Boulevard, the South Padre Island Police Department reported. The victim was treated on scene for a shark bite to his leg before he was transported to a nearby hospital, police said.

Also shortly before 11 a.m., video obtained by CBS News showed police rushing to the scene of a woman who was bitten on her left leg by a shark while swimming.

The video showed Good Samaritans and first responders pulling the woman from the water and wrapping a tourniquet around her leg to slow the bleeding. A dorsal fin can be seen swimming back and forth near the shoreline. 

"Pending investigation, we do not know the species, we do not know the reason why this is happening, it's unprecedented right here on South Padre Island," Pigg said. 

Dr. Kelsey Banks, an associate research scientist with the Center for Sportfish Science and Conservation at Texas A&M University-Corpus Christi, told CBS News in an email that the video posted to social media suggested a "larger shark species."

"Larger coastal species have been known to increase feeding behaviors and remain closer to shore prior to large meteorological disturbances," Banks wrote. 

In response, officials quickly deployed drones, boats and a helicopter to search for sharks. The city said it was considering closing the beach to the public, a Coast Guard lieutenant confirmed to CBS News. 

South Padre Island is a 113-mile-long barrier island, off the southern tip of Texas, known for its resorts and beaches.

— Manuel Bojorquez contributed to this report. 

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• Texas