Guidroz, the sheriff, spoke of the difficulty of informing deputy Roy Matthews about his son's alleged involvement in the fires.
"When Matthews was developed as a suspect we saw an immediate threat to public safety", Mr Browning said.
The churches were empty at the time of the fires, and no one was injured.
Several black churches in the South were burned in 2015 shortly after the mass murder of nine people at the Mother Emanuel African Methodist Episcopal Church in Charleston, South Carolina, though it is unclear if those fires were racially motivated. The fire marshal said the genre has a history associated with church burnings.
"Holden Matthews' father did not turn him in", Guidroz said.
Many residents said the church burnings brought back memories of civil rights-era violence.
"There's still people that need to be helped, there's still ministry that has to be done, so we can't let this setback stop us from doing what God has initially called us to do", said Pastor Kyle Sylvester of St. Mary's Baptist Church.
The charred remains of a red gas can recovered at one of the churches was sold at Walmart locations, and the company's investigators found that the same type of gas can was bought March 25 at a store in Opelousas, along with automotive cloths and a lighter.
The younger Matthews was arrested on three counts of simple arson of a religious building.
U.S. Attorney David C. Joseph says authorities have arrested a person in connection with suspicious fires at three historic black churches in Louisiana.
The arson attacks targeted three historically-black churches - St Mary Baptist Church in the city of Port Barre, Mt Pleasant Baptist Church in Hammond, and Greater Union Baptist Church in Opelousas.
Just one week after a black/death metal musician was arrested for starting multiple church fires in New Zealand, it has happened again - this time in the United States in the state of Louisiana.
Louisiana State Fire Marshal Butch Browning told reporters on Thursday that each of the three counts against the suspect carries a sentence of up to 15 years in prison.
Governor John Bel Edwards said the fires were "especially painful" because they were a reminder "of a very dark past of intimidation and fear". Black metal music by popular groups such as Behemoth and Gorgoroth often contains lyrics that embrace satanism and paganism.
A Facebook page that appears to belong to Mr. Matthews shows him with the words "black metal" spray painted on a wall behind him.
Mt. Pleasant Baptist was more than 140 years old, according to Rev. Gerald Toussaint.
"This is not going to be music that is studied listened to or performed in 100 years the way our great masters are", Grimes said.
Louisiana state authorities have been investigating the three fires alongside officials from the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), a federal law enforcement organization within the U.S. Department of Justice.