Macro with !shoot

I have been trying to make a macro with a simple castsequence and ending with !shoot
failing miserably…
I use a key repeat, so im holding button down…
no matter what i do i can not get it to shoot at the end, it just wants to toggle or spaz out on me.
Any way I can get it to shoot once regardless, till mob dead?

/targetenemy [noharm,dead]
/castsequence reset=target/combat Corruption, Immolate, Shadow Bolt, null

Step 2
/castsequence reset=target !Shoot, null