If a wicked man seems to have peace at death, it is not from the knowledge of his happiness, but from the ingnorance of his danger.
Isaiah 55:6 states:
Seek the Lord while He may be found; call upon Him while He is near.
When death comes it is too late. The dead, unrepentant, sinner may seem to be at peace but it is only because he is not there. He has gone on to meet his due reward for not trusting in Jesus Christ. The bible calls this the second death, a total separation from God.
Oh sinner, call on the Lord today. Seek Him while He may be found.