The hate of hate
Hate is jealousy – jealousy come from the one who feels already depressed and is sad at the happiness of others.
Hence the shooter at the Sikhs knew he would be killed.
We need to understand – if people desire life, why would they kill if they too will be killed?!
The answer is, that the depressed person actually has no hope – therefore he already is dead! as our sages state, the evil are dead while alive.