I murdered all of my friend's goldfish.
Why would you do something like that to your friend?
They have been disrespectful towards me
I know your friend may have wronged you, but this was not the right way to go about things. If you had issues with your friend you should've talked to them and see what you could've done the work it out.
My friend was disrespectful, not the goldfish.
Regardless of that fact it still wasn't right to take revenge on your friend's goldfish. Like I said you should've approached your friend about the issue and worked it out via communicating. You need to be honest if your friend about what happened.