When you want to play a certain animation you will need to script it or replace the death animation within the fpe to whichever frames your new animation is. For instance I want the head to pop off when I shoot the character so I would change the script to play that animation like so using the appearwithheadshot.fpi " state=0:setalphafade=100,headshot=1,runfpidefault=1,animate=1 " or if you were using fenix mod you would simpily type " shotinhead=1:removehead " if I remember right.
If you want to make like a glass break or trash to pop out of a trash can, you would just use the destroyandactivate.fpi to spawn the new entities or if it is like a door that has animations to react to being shot you would put " shotdamage=90,animate=1 " or whatever to play that animation, but you need the entity to be dynamic and have alot of health so that if the plr continues to shoot at it you would need to keep it there in that frame or script it so that after the shotdamage that it stays alive.
I hope this helps for both of you.
All of it is simple to do, but takes some time to setup.