Appendium, and one I can't attest to from personal experience, but if the shooter is up high and resting on a railing or some-such, running towards the direction of the shots might offer a better chance of survival. [if no cover is available].

Bullets can go a long way, but guns can only be angled downwards so far. Get in under his cone of fire and you stand a better chance. [not a good one, just better]

Or at least, so an SAS buddy of Grandfather told me... OTOH, they are crazy-ass sods, so usual disclaimers apply. [he also said that if you do get killed, at least it looks like you were trying.]