Baruch Dayan Ha'emes is the brachah associated with bad news. More specifically, it has become known as the brachah to say when hearing of the news of someone's passing.
Is it appropriate to say Baruch Dayan Ha'emes when someone commits suicide? On the one hand, someone Jewish died. On the other hand, the person who died killed someone, and their death was itself an act of retzichah.