Is it a realistic fear? Probably not. It's highly unlikely you'll ever be killed by a police officer, especially if you're not a criminal (although that doesn't seem to stop plenty of cops). I have mostly black friends, I can't say any of them ever express this same fear, even when we speak openly about race. Some of them are much more worried about being killed by people who live in our own neighborhood.
If you're frightened of dying, and you're holding on, you'll see devils tearing your life away. But if you've made your peace, then the devils are really angels, freeing you from the Earth.