I'm sorry to hear this, but sadly I'm not surprised at all. The sad reality is that tourists should not walk alone in the evenings, especially by the beach. I feel ridiculous saying this, as the authorities here should be able to prevent this sort of thing from happening.

One piece of advice though: do not ever EVER chase them. An Italian tourist did that last week and is going home in a coffin. Just let them go and feel lucky all they got was your i-Phone.