Teenager killed in Florida shark attack

The St. Pete Times has an article as well and references the International Shark Attack File.

According to the Times article, a witness reported the shark appeared to be a bull shark. According to the ISAF's page on bull sharks:

Danger to Humans

According to the International Shark Attack File (ISAF) bull sharks
are historically responsible for at least 69 unprovoked attacks on
humans around the world, 17 of which resulted in fatality. In reality
this species is likely responsible for many more, and has been
considered by many experts to be the most dangerous shark in the world.
It's large size, occurrence in freshwater bodies, and greater abundance
in close proximity to numerous human populations in the tropics makes
it more of a potential threat than either the white shark or tiger
shark. Since the bull shark occurs in numerous Third World regions
including Central America, Mexico, India, east and west Africa, the
Middle East, Southeast Asia, and South Pacific Islands, attacks are
often not reported. The bull shark is also not as easily identifiable
as the white or tiger shark, so is likely responsible for a large
percentage of attacks with unidentified culprits.

Read more here.