A historic church in southwest Atlanta was found vandalized Monday while its members were celebrating Martin Luther King Jr. Day.

Isaiah Waddy, the pastor of Saint Paul African Methodist Episcopal Church, told Channel 2 Action News it was the first incident of its kind in the nearly 56 years the church has been on Pryor Street.

They called Atlanta police Monday afternoon when “666” and “pay back” were discovered spray-painted on several front windows and a brick wall.

“It was disturbing to me because it was Martin Luther King celebration day,” Waddy told the news station.

Several church members spent the afternoon cleaning up, and “everybody just kind of left sad and somber,” he said.

While Waddy can make some guesses about the meaning of the numbers painted on the church, he said he does not know what “pay back” could be referencing.

He encouraged whoever was responsible to come back to Saint Paul, this time to join the congregation inside.

“Please come back on Sunday and worship with us,” Waddy said. “You don’t have to say, ‘I was the one did it, just come in.'”

Police confirmed to Channel 2 they are investigating the incident as a criminal damage to property.