As authorities investigated the weekend firebombing of a Republican Party office in North Carolina, supporters from across the political spectrum rallied behind the victims.

That included a Democratic tech writer in Boston who started a GoFundMe page to raise money to help the Orange County Republican Party recover from the attack, which destroyed the group's headquarters in Hillsborough but did not injure anyone.

The organizer, David Weinberger, said he and some other Democrats, along with some independents, started the campaign "because we believe that in order for our democracy to survive, we have to work against the violent force that want to disrupt it." By Monday morning the campaign raised more than $13,000 from more than 500 donors.

Fire damage at the Republican Party office in Orange County, North Carolina.

Who did it, and why, remains a mystery. But the attackers seemed bent on causing a lot of damage — and fear. The fire was caused by a flammable bottle thrown through a window of the office sometime overnight Saturday, authorities said. On the outside someone wrote "Nazi Republicans" and "leave town or else," adding a swastika.

Graffiti on the extrerior of the Republican Party office in Orange County, North Carolina.

Federal agents are helping local authorities investigate.

North Carolina Republican Party spokeswoman Emily Weeks told NBC News that the office was destroyed, along with materials inside, which may have included some completed absentee ballots. The operations will be relocated to a bus that will serve as a mobile office.

The head of the North Carolina GOP called the bombing a hate crime and a "violent attack against our country." He asked that all local Republican officers close at sundown.

Republican presidential nominee Donald Trump blamed — without proof — "animals representing Hillary Clinton and Dems in North Carolina."

Clinton condemned the attack as "horrific and unacceptable."