You know this is a very good question.I've been wondering the same myself.
When I gave it some thought and took a look at one of the shoot scripts,I came to a conclusion,yes you can.However you would need a custom script for the enemies.The default ones will need way too much editing.
Essentially what you need to do is add a few lines of code which will determine wether the player was shot or not and then remove from his health.Also you'll need to command the entity to draw and shoot his weapon.
:state=1,ifweapon=1:rotatetoplr,settarget,useweapon,state=2
:state=2,random=2,rateoffire:plraddhealth=-12
:state=2,random=3,rateoffire:plraddhealth=-14
:state=2:state=1
So to brake this down,after the weapon is being shot , if a random number from 1 to 3 is x then plrhealth is substracted by 14 (or 12 for 1 to 2 for variety in damage).Then immediately the script tells the state to switch back to 1 to shoot the player again.This is a loop and every time the gun is shot it's checked randomly for accuracy
This should give you an idea how to achieve what you want
