They usually come under the shroud of darkness, late at night when no one is around, and approach the shrines as assailants.
They leave behind relatively minor physical damage -- hands dislodged from a wooden statue of the Virgin Mary, or statues toppled into pools. They defaced walls in one instance and burned a church pew in another.
But the insult runs deep, scarring the souls of the faithful.
"It's become an issue," said Father Richard Kennedy, pastor of St. Barbara's Catholic Church in Santa Ana, one of three Orange County parishes that have endured a string of apparently unrelated vandalism attacks in recent weeks. "Different [parishioners] come up and say they want to pay for surveillance and stuff like that. They get pretty upset."
Vandals have struck at St. Callistus Church in Garden Grove, causing minor damage by setting fire to a pew, and at St. Barbara's and Our Lady of La Vang in western Santa Ana, where icons and statues have been damaged or stolen.
Police and church officials believe that the incidents are unrelated and that each church's problems are isolated. They do not consider them hate crimes.
"We have absolutely no leads as to who may be responsible," said Santa Ana Police Sgt. Baltazar De La Riva. "There are differences in the way the crimes are being committed. Up to this point we don't have any evidence that would lead us to believe these incidents are related."
Garden Grove Police Lt. Mike Handfield, whose department is investigating the pew burning at St. Callistus last week, said he hopes to meet with an interfaith council to try to learn whether other acts of vandalism have gone unreported.
"We're just going to be making sure all these things are reported so that we have a good idea of what's going on," he said.
Kennedy said the incidents at his church -- at least five -- have led him to consider installing video surveillance, hoping to catch on tape whoever is vexing his parish.
But he said the incidents won't lead to changes in access to the church, where the doors are left unlocked during the day so the faithful can enter for prayer.
"I have a feeling that whoever is doing it is a little cuckoo," said Kennedy, taking the damage in stride. "It's only a statue. It's not as if they were breaking my hands off."