Saint Peter Martyr was a Dominican friar and an Inquisitor. In 1252 he was murdered in a wood by heretics. He accepts his murder (foreground) for the cause of Christ (angels appear above his head with a martyr's palm). His colleague (right) was also attacked and wounded but escaped.
This was once famous as a painting by Giorgione but is clearly from a later period. The subject was famous in Venice from its treatment by Titian in an altarpiece for SS. Giovanni e Paolo.