DURHAM, N.C. — The Secret Service Monday joined the FBI, local police and the Bureau of Alcohol, Tobacco, Firearms and Explosives to investigate the firebombing of a North Carolina Republican office, the Hillsborough Police Department announced Monday afternoon.

Sometime between midnight and 8:54 a.m. Sunday morning a bottle containing a flammable substance was thrown through the front window of the Orange County Republicans headquarters and ignited inside the building, according to authorities. A swastika was spray painted on an adjacent building with the message “Nazi Republicans leave town or else.”

“In a town like this, stuff like this doesn’t happen,” said Bennie Sparrow, who called police when she saw the message on the side of the balloon shop she has owned for more than 30 years. “This is supposed to be a happy place, it’s not supposed to be hate-filled, and that’s hate.”

The GOP building has not been cleaned up, with charred walls, glass shards on the floor and heavy fumes from the burnt plastic and gas. The graffitti on Sparrow’s shop had been painted over.

The aftermath of the firebombing at the Orange County Republican office.

The aftermath of the firebombing at the Orange County Republican office.

“This highly disturbing act goes far beyond vandalizing property; it willfully threatens our community’s safety via fire, and its hateful message undermines decency, respect and integrity in civic participation,” Hillsborough Mayor Tom Stevens said in a statement.

Daniel Ashley,  chairman of the Orange County Republican Party, learned about the attack he called “political terrorism” Sunday morning when he came by the office and saw police tape around his building.

“My first reaction was anger,” said Ashley. “Anger that somebody would try to silence our right to vote, our right to belong to the party that we chose to belong to.”

Bill Knight, who has headed the country GOP three times, set up outside the burned office Monday, making phone calls and putting together yard signs. The plan is to reopen in the another office in the same strip mall until the current office is rebuilt.

“We’re back in operations and we will be until November 8,” he said.

Orange County is perhaps the most liberal in the entire state, having voted Democratic in the past six presidential cycles. In 2012, when Mitt Romney won the state over Barack Obama, Obama still received more than 70 percent of the county’s vote.

Blake Halsey, a student at Methodist University in Fayetteville, North Carolina who volunteers for the Orange County Republicans, said he’s grateful for the support from Democrats and Republicans since the bombing.

“We’re not scared at all,” he said. “We’ve received support from all sides. We hope this will unify all the campaigns. I wouldn’t want this to happen to the Democrats, the Libertarians, Independents, anybody. It’s just downright awful.”

David Weinberger, a Democrat, started a campaign to rebuild the Republican office on GoFundMe, a crowdfunding website. The campaign met its goal of $10,000 in less than one hour and has currently raised over $13,000.

“It certainly seemed to tap into a thirst for decency and civility and even safety in our democratic processes,” he said.