As they all told you, it's an Olive, not a cone or cowry. They are predatory, although they also scavenge. Mokeyz gave you the names of the two most deadly cones, both of which have venom containing powerful neurotoxins that affect vertebrates. There are a lot of others that are potentially deadly, but most of them either have very small teeth, making it difficult to envenomate a human, or they don't live in shallow water where they are likely to be collected by novices. The one possible exception is Conus textile. It's generally considered to be a mollusc eater, but researchers have found that the venom composition varies depending on where the animals were collected, with those from some areas (Australia, I believe) producing toxins that are potentially deadly to humans. The majority of cones are worm eaters, and those don't pose much of a threat to humans since the neurological systems of worms and vertebrates are very different.
Cheers,
Don