Vandals struck an anti-abortion group’s office in Wisconsin, apparently setting a fire after a Molotov cocktail thrown into the building failed to ignite, authorities said.

Flames were seen coming from Wisconsin Family Action’s office shortly after 6 a.m. Sunday, and the fire was being investigated as arson. It wasn’t immediately clear who vandalized the building, but the message “If abortions aren’t safe then you aren’t either” was spray-painted on the exterior.

“It appears a specific nonprofit that supports anti-abortion measures was targeted,” Madison Police Chief Shon Barnes said in a statement. Police planned a Monday afternoon news conference to provide an update on the investigation.

The vandalism came days after the leak of a draft opinion suggested the U.S. Supreme Court was on course to overturn the landmark Roe v. Wade decision that legalized abortion. The leak spurred immediate demonstrations, including weekend protests by abortion rights supporters outside the homes of conservative justices, with more planned this week.

The president of the lobbying group, Julaine Appling, said she considers the fire a “direct threat against us.” She said people could have been hurt if they had been working in the office at the time.

“This is the local manifestation of the anger and the lack of tolerance from the pro-abortion people toward those of us who are pro-life,” Appling told the Wisconsin State Journal.

Appling said her group won’t be intimidated.

“We will repair our offices, remain on the job, and build an even stronger grassroots effort,” Appling said. “We will not back down. We will not stop doing what we are doing. Too much is at stake.”

Politicians from both parties swiftly condemned the vandalism.

“We condemn violence and hatred in all forms, including the actions at Wisconsin Family Action in Madison,” Gov. Tony Evers, a Democrat, said in a tweet. “We reject violence against any person for disagreeing with another’s view. Violence is not the way forward. Hurting others is never the answer.”

The governor said Monday during a question-and-answer session with reporters at a pharmaceutical company groundbreaking in Verona, a Madison suburb, that the incident was “horrible” and whoever is responsible should be arrested and put on trial.

“This is unacceptable,” Evers said. “Violence does not solve the issues we’re facing as a country.”

Sen. Ron Johnson, a Republican, said the actions shouldn’t be tolerated.

“This attack is abhorrent and should be condemned by all,” Johnson said.

Clinics that perform abortions have sometimes been targeted by vandals, too, including as recently as January when a Planned Parenthood clinic in Tennessee was hit by arson.