By CBSLA Staff

NEWPORT BEACH (CBSLA) — A thresher shark was euthanized Friday after coming onshore with possible boat propeller injuries.

Beachgoers scattered after the shark came onto shore at about 1:45 p.m. Friday near Balboa Pier. The shark was seen thrashing on the shore as people in bathing suits and holding boogie boards watched quietly.

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The 3- to 4-foot thresher shark appeared to have injuries consistent with being hit by a boat propeller.

State officials said within the last five days, four thresher sharks from Newport Beach to Santa Cruz have stranded themselves, and many sharks are also dying from brain infections, which a marine biologist suspects to have been the case for this shark before it was physically injured.

“What we found is the infection of a bacterium in their brain. That bacterium actually starts to eat away the brain and it kind of turns the sharks into zombies,” said marine biologist Chris Lowe. “They become disoriented and swim themselves into shore, where they get stranded. A lot of the time the public finds them and tries to push them back out (into the water), but those sharks, unfortunately, are going to die.”

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Several lifeguards helped pull the barely-alive shark out of the water.

Holly Attea, who shot the incident on her cellphone, says that lifeguards warned swimmers to get out of the water and for the people on the sand to stand back.

“We were hoping it would swim back out but it just wasn’t, it would swim back out and then come back in and lifeguards were trying to save it,” she said.

Animal control officers said due to its injuries, the shark had to be taken into their custody and was later euthanized.

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It is unclear exactly what brought the shark to shore but a necropsy, which could be completed by Monday, is expected to shed some more light on its injuries and condition.