OPELOUSAS, La. — The 21-year-old son of a deputy sheriff was charged in connection with the burning of three predominantly black churches in St. Landry Parish, La., the authorities announced on Thursday.

The arrest of the deputy’s son, Holden Matthews, came about two weeks after the first fire, which evoked the racist imagery of the Jim Crow South and set on edge a Cajun community with a large black population and deep Christian roots.

The three blazes took place within a span of 10 days, destroying churches that had been around for more than a century and had been the spiritual homes of generations of black families.

At a news conference announcing the arrest and charges of three counts of simple arson of a church building, Gov. John Bel Edwards of Louisiana said that although he did not know the motivation behind the fires, “these were evil acts.”