Actually, the usual MO is to casually approach on the sidewalk as if just walking the other direction, then swing without warning.
IOW, it's a surprise attack and the only way to prevent it by armed action is to shoot before the attack starts, which would be considered utterly unjustified in every state in the country. Or be fast enough to dodge the swing, draw and fire. Which is I suppose possible.
The most likely outcome of this story is that some white person will shoot a black guy he/she thinks is planning such an attack. Possibly accurately, maybe not.
It will be claimed the black guy was utterly innocent, and it might even be true. Mass moaning and wailing over "walking while black" will follow.
Stay out of range...