Most of my examples are God doing things. Who else made the world-wide flood, for example? Who killed every firstborn son and calf in Egypt? Perhaps the genocide cannot be directly attributed to God, but everything else can.
These aren't a question of God stopping sad things from occuring, it's a question of God causing these sad things to occur. I don't see how a world-wide flood is a natural event, nor each first-born son dying through God's orders. That's not natural, that's through God's orders.
OT was written in such a way that God's sovereignty is always emphasized. As a result, you may find that it's said the devil did something while in another chapter regarding to the exact same event it's said God did that.
Will you show the verse where first born sons are killed? I never read that humans are sacrificed actually. I think ancient Jews can sacrifice animals for any needs.