Ambridge, Pennsylvania - A potential mass shooting attempt was foiled at a majority-Black church in Ambridge, Pennsylvania, on Sunday – just one day after a white supremacist gunman opened fire at a Dollar General store in Jacksonville, Florida.

A white man armed with a 12-gauge shotgun was denied entry to Ambridge's Greater Dominion Church on Sunday in what authorities believe may have resulted in a devastating racist attack had he been admitted, the Atlanta Black Star reported.

The 38-year-old man, Jeffrey Harris, reportedly raised his shotgun at two women standing at a nearby intersection after he was denied access to the church. The women called the police, sparking an investigation into the incident.

Police eventually disarmed and detained Harris, who was discovered in possession of crystal meth at the time of his arrest.

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At Harris' home, officers found the porch covered in lubricant, a stash of weapons, more crystal meth, and a letter detailing plans to carry out a mass shooting. A bomb squad was called in to deactivate a suspected explosive.

Bishop Kenneth Crumb said in an interview with WTAE-TV that Harris was denied entry because the church was full and would have been admitted had he come just an hour later.

"When you just think about how close we came to having the same kind of horrific situation that we had at the synagogue in Pittsburgh, it’s like the Grace of God. Thank God for his grace, for his covering over us, because this could have been a total different way," Crumb told the station.

"There is a whole lot of mass murders going on, there is shootings, particularly in the African-American community, people targeting our communities," he added.

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The averted attack came just one day after a white gunman killed three Black people at a Dollar General before taking his own life in Jacksonville, Florida, in what authorities have described as a clear hate crime.

A hearing in Harris' case is set for September 5.