The U.S. Justice Department has charged a neo-Nazi leader and his associate with plotting to attack Baltimore’s power grid, a plan the FBI thwarted with the help of a confidential informant.

Brandon Russell, of Orlando, Florida and Sarah Clendaniel from Maryland, were arrested last week, officials said in a briefing on Monday, and they have been charged with conspiring to damage an energy facility.

Russell is a convicted felon and founder of a neo-Nazi group called the Atomwaffen Division that works toward “ushering in the collapse of civilization,” according to the Southern Poverty Law Center, a civil rights organization that tracks U.S. hate groups.

Russell previously was sentenced to five years in prison after pleading guilty to possession of an unregistered destruction device and the improper storage of explosive materials.

At the time of his arrest, he was still on supervised release, according to the FBI.

The FBI on Monday alleged the plot was racially motivated but did not provide details. About 62% of Baltimore city residents are Black, according to U.S. Census data.

Representatives for Clendaniel and Russell could not immediately be reached for comment.

“Clendaniel and Russell conspired and took steps to shoot multiple electrical substations in the Baltimore area aiming to ‘completely destroy this whole city’, but these plans were stopped,” Erek Barron, the U.S. Attorney for the District of Maryland, said in the press briefing.

Russell first came under suspicion in 2017, when his former roommate Devon Arthurs was arrested for murder.

During his interview with the FBI, Arthurs said his fellow roommates were plotting to attack U.S. infrastructure, including power lines in Florida.

The information led to Russell’s arrest and subsequent conviction.

Then, starting in at least June 2022, an FBI confidential informant started to receive encrypted messages from a user known as “Homunculus” who encouraged the informant to attack electrical substations, the complaint says.

In those communications over the next few months, Homunculus urged an attack “when there is greatest strain on the grid,” and noted that follow-up attacks could further lead to a “cascading failure costing billions of dollars.”

In January 2023, as their communications continued, a third user known as @kali1889 joined the conversation. She said she had compiled a list of potential targets, including Baltimore, noting the location was “literally like a life artery.”

According to the complaint, the account @kali1889 was traced to Clendaniel, who also has an extensive criminal record including a prior conviction for armed robbery.

“Homunculus,” meanwhile, was traced back to Russell, the FBI said.

Baltimore Gas and Electric, a subsidiary of Exelon Corporation EXC.O, which owns the targeted substations, said there was no damage to any of its equipment or outages.

The arrests followed recent vandalization of electrical substations that left thousands of people without power in other states including North Carolina, South Carolina and Washington.

The motives for those attacks were not known.

Thomas Sobocinski, the special agent in charge of the FBI’s Baltimore office, said the FBI was not aware of any links between the two people arrested in the alleged Baltimore plot and attacks elsewhere on electrical infrastructure.

In Tacoma, Washington, four electrical substations were vandalized around Christmas, leaving over 14,000 customers without power. Two men were arrested in connection with those attacks.

Also in December, a utility in North Carolina reported outages from what local authorities said were orchestrated shootings investigated by federal law enforcement. Duke Energy Corp DUK.N, which provided power to the area, said at the time a total of 45,000 people had lost power.