What does "a change of heart" mean in the following newspaper article? Is there any difference between "a change of heart" and "a change of mind?"
Mr. Comey’s willingness to discuss the threat in public was something of a change of heart. As F.B.I. director, he supervised counterintelligence investigations into computer break-ins that harvested emails from the State Department and the White House, and that penetrated deep into the computer systems of the Joint Chiefs of Staff.
Source: New York Times