An abortion-rights group calling itself "Jane's Revenge" claimed responsibility for Sunday's fire attack on the offices of the anti-abortion nonprofit Wisconsin Family Action.
The group said it would not hesitate to strike again if there were any more anti-choice organizations or fake clinics.
The group accused anti-abortion groups of bombing clinics and killing doctors with impunity.
The Jane Collective, a Chicago-based group that helped women obtain abortions, is said to have been referred to as Jane's Revenge.
Evans said that the unnamed source of the message has a reputation for extreme reliability, but that he was not directly in touch with the purported members of Jane's Revenge.
The local police were aware that a group had claimed responsibility for the attack and were working with federal partners to investigate the validity of the claim.
The Bureau of Alcohol, Tobacco, and Firearms was aware that Jane's Revenge had claimed responsibility, but were not able to provide more information about the investigation.
The message from Jane's Revenge didn't mention the leaked Supreme Court draft opinion that would overturn the 1973 ruling that legalized abortion.
Madison fire officials said that a fire at the office of Wisconsin Family Action was quickly extinguished. A molotov cocktail was thrown inside the building during the attack, but it did not catch fire, and the person who started the second fire was the same person who threw the molotov cocktail. There is a spray-painted message on an outside wall that says if abortions aren't safe then you aren't either. Tony Evers, the governor of Wisconsin, said that attempts to limit abortion rights should be met with "empathy and compassion".
There is no evidence that a group called "Jane's Revenge" existed or that it was responsible for the Wisconsin attack.
The Wisconsin Anti-Abortion Office was targeted in a suspected Arson attack.