I'm going to tell people that my partner's boss leaked information about a murder.
Why are you going to tell people that their boss leaked information about a murder?
He's a bad person and I want people to know what he did.
It sounds like your partner's boss was doing exactly what he should've.  A murder is a serious crime and anyone who knows anything about it should report that information to the authorities.
I don't give a shit and he will pay.
Your boss is only trying to be a good guy and saving a family from grief. A murder is something really wrong and they deserve to be solved right away. I hope you can come to understand that.