Thank you for your Question.
Alhamdulillah, your question itself shows that you still have this very kind and polite side that wants to put away this cruel act.
It is indeed very sad to treat such little souls this way. More so because they can’t even complain regarding it to anyone. However the one they are complaining to is the one who has all your affairs in HIS hands too.
They are complaining to someone who has all power over everything, Allah (swt)
This is indeed a test whether you fear Allah or not. If there was a cctv camera in your room, would you treat the kittens the same way!?
Then why should it be different when Allah is all-Hearing and all-Seeing! وَهُوَ السَّمِيعُ الْبَصِيرُ: 11:42
If you feel you can not control your anger and keep on doing this, kindly take them away from your office and put them somewhere where they will be more safer and happier InshaAllah
Hope this is solved