Now Herod the tetrarch heard of all that was done by him: and he was perplexed, because that it was said of some, that John was risen from the dead;
Note 1 at Lu 9:7: Others may have thought Jesus was John the Baptist risen from the dead, but as can be clearly seen from Matthew's account (Mt 14:2) and especially Mark's account (Mr 6:14-16), Herod was convinced of this personally. This illustrates Herod's conviction of his sin that John rebuked (Mr 6:18), his guilt and torment over his even greater sin of beheading John (Mr 6:27), and his fear of John and the God he represented (Mr 6:20). Also revealed in Mr 6:20, Herod listened to John gladly. It is certain that John was preaching his favorite message of "Repent ye: for the kingdom of heaven is at hand" (Mt 3:2). For Herod to hear him gladly, he must have been under deep conviction from God.
However, as can also be seen, Herod feared his wife (Mt 14:3) and the opinions of others (Mr 6:26) more than he feared God (Pr 29:25). Herod was not as Festus, who told Paul he was mad for speaking of the resurrection from the dead (Ac 26:24). Herod knew the truth personally, was exceedingly sorry, and yet chose death, both John the Baptist's and his. Apparently, as can be seen in this instance, Herod had not had any peace since his fatal choice. "There is no peace, saith the LORD, unto the wicked" (Isa 48:22).