What's your move when someone is behind you shooting you as you run?

My current approach is to panic. But it's not working well.

Seriously though, this one gets me a lot. I'm running. Someone appears behind me and starts firing. I try to dodge. I try to turn around. I try to jump. Rarely ends in my favor.

Any tips?

UPDATE: Thank you all for the fantastic advice. Trying these things should make it much more interesting for you when you're destroying me in Team Slayer :)

Appreciate the help!