On Pentecost Sunday, May 21, 1972, a geologist with a history of mental illness climbed over a barrier inside St Peter's Basilica and attacked the Pieta with a hammer, striking Mary's face and left arm roughly a dozen times before onlookers and guards could stop him. He shouted, in the accounts of witnesses present, that he was Jesus Christ, risen from the dead. The attack damaged Mary's nose, chipped one eyelid, and broke her left arm at the elbow, sending fragments of five-century-old marble across the basilica floor, some later recovered from among the crowd of pilgrims and visitors present that day.
The Vatican's response combined an extensive, closely documented restoration with a lasting change to how the sculpture is displayed. Restorers spent roughly ten months reassembling and repairing the damaged sections, using detailed photographic records taken before the attack to guide the reconstruction as precisely as possible, and the repaired sculpture was placed back on public view the following year. Since then it has stood behind a barrier of bulletproof acrylic glass, a protective measure common today for the world's most vulnerable and heavily visited artworks but far less standard practice at the time of the attack itself.
The attacker, found to be suffering from a serious psychiatric condition rather than criminally responsible in the ordinary sense, was committed to psychiatric care in Italy rather than imprisoned, and was eventually deported to his native Australia. The Pieta itself, chipped and repaired but recognizably whole, remains one of the most visited works of sculpture in the world.