We don't really know yet. Researchers believe it may also be happening on the eastern seaboard of the U.S. Researchers at the Virginia Marine Science Museum have been documenting similar occurrences. The aggressive behavior being reported now with dolphins is indicative of the social behavior of some species of large mammals. For example lions and bears exhibit similar aggressive behaviors towards young of their own species or other animals. We don't know.
Intelligence is very difficult to measure even with human beings.
Scientists believe that dolphins like other social mammals possess a degree of intelligence similar to chimps. And they certainly possess a large brain relative to their body size. The behavior of dolphins in the wild is unpredictable. They can bite, hit, and body slam people who try to feed or interact with them. There have been several documented cases of wild dolphins injuring people.