How was John Nichols finally forced to believe that sharks could be deadly to humans?

Hearing about the attacks, ichthyologist John Nichols drove from New York City to the Matawan Creek. He stopped at the mouth of the creek where the shark would have to leave to return to the open waters. Nichols still maintained that an orca was responsible for the attacks. He soon realized that the size of the creek would not accommodate a killer whale. Eyewitnesses described the physical features of a shark when Nichols interviewed them.