If God is dead, man also is dead. At most, he becomes merely a configuration of molecules. Freedom is an illusion. He is both an accidental product and victim of circumstances. Like an organ stop, he cannot act but only react.
Life is then a journey toward nothing.
And that which ends in nothing is worth nothing. Death rises up to crush him like a discarded cigarette butt under the heel of a meaningless universe. That is not all. Without God there is no basis to affirm a moral order, no reason to say that one action is right and another wrong. If death ends all, then in the final analysis it doesn't make any difference whether I wring my neighbor's neck or shake his hand.