Regan Darby Prater, 28, also received three years of supervised release after prison, according to the U.S. Department of Justice. He pleaded guilty in April to arson and attempting to provide material support to Hezbollah, which the United States designates as a foreign terrorist organization.

Prater admitted driving from his home in Tullahoma to the center in New Market on March 29, 2019, and setting off a napalm-based incendiary device known as a “sparkler bomb.” The fire destroyed an administrative building and caused more than $1.2 million in damage.

Before setting the fire, Prater spray-painted an Iron Guard symbol in the parking lot. The Iron Guard was a Romanian fascist paramilitary organization in the 1930s; the same symbol was engraved on the weapon used in the 2019 Christchurch mosque shootings in New Zealand, two weeks before the Highlander fire.

The center said the blaze also destroyed decades of historic materials, including documents, speeches, artifacts and memorabilia from the civil rights movement. Highlander is a social justice education and research organization with a long history of training civil rights activists. Martin Luther King Jr. and Rosa Parks were among its visitors.

In his guilty plea, Prater also admitted trying to provide information to someone he believed was connected to Hezbollah. He obtained a document that purported to contain personally identifying information for more than 35,000 people affiliated with the Israeli government and sent it with the message, “Start the hunt,” according to the Justice Department.

The FBI investigated the case with assistance from the Tennessee Bureau of Investigation.