For a 3D top-down game, how should I handle collision in melee combat? My game has no targeting system, so I can't use a simple distance check between attacker and target. 

What I am thinking is have the character swing, generate a hit box, run the damage script for any characters in that hit box, and then delete the hit box. How should I handle this?

Also, I would like to use the same attack script for all players and NPCs in melee, even with different attack animations and hit boxes. However, really I can't figure out how to reliably assign who the attacker and who the target are within that script, or how to handle multiple simultaneous attacks.