Can you be cautioned for criminal damage if the damage was done to your own property?

My son punched his own freezer causing a dent.This happened on a Friday due to frustration not temper. His partner was present but was not in anyway under threat. He left his partner on Sunday after having enough. She then reported incident to police. He had call to go to police station, he went and admitted what he had done saying its his own property. They let him go saying all was ok. Next thing he had phone call saying he was being cautioned with criminal damage, he was fingerprinted etc , then told it would be on his record for 5 years. Is this correct?