I suspect the culprit was a bull shark

A juvenile Great White may have been responsible for the ocean attacks but a bull shark probably killed Lester Stillwell in Matewan Creek. It was previously believed Matewan was freshwater or brackish. Great Whites tend to avoid such areas. However author Richard Fernicola later explained that the creek was salt water based according to his research. A young white shark could have swum into the creek and become trapped but the frequency of the attacks and the aggressiveness suggest a different type of shark ie the bull shark.