Hello webslinger21,
Here are some guidelines to achieve it:
1. You need to make an enemy model with a gun.
2. Check if the player is near the enemy and then make the enemy shoot the player if so.
3. In order to shoot the player, the enemy needs to spawn a bullet (could be a sphere) and use the impulse command towards the player/camera.
4. If the bullet hits the player (if collision), you need to update the player lives, etc...
Please tell us if you succeeded or need more help.
Regards,
Cyberix3D team