Last September, as two would-be kidnappers made their way to the vacation home of Michigan Gov. Gretchen Whitmer (D) for nighttime surveillance, the pair made a pit stop at a nearby highway bridge, according to prosecutors.

Then the two members of an extremist anti-government group, Adam Fox and Barry Croft, allegedly looked for the optimal spot to “mount an explosive charge” underneath — all so they could blow the bridge up to stall police trying to reach Whitmer’s home.

The kidnapping plot never came to fruition, as Fox, 40, Croft, 45, and other extremist group members were arrested and charged in October. Now, the pair and one other defendant, Daniel Harris, 23, face new charges, including conspiracy to use weapons of mass destruction and federal firearm violations, in the newly detailed scheme to explode the bridge.

“The defendants engaged in domestic terrorism,” said an indictment filed on Wednesday after a grand jury in the Western District of Michigan court added the new charges.

Croft’s lawyer, Josh Blanchard, said in a statement he was “looking forward to defending the case in court this fall.” Lawyers for the other defendants did not immediately respond to requests for comment.

Federal prosecutors rarely distinguish violence or threats from extremists in the United States as domestic terrorism because there is technically no federal domestic terrorism law. But after the insurrection on Jan. 6, and amid a rise in threats from right-wing extremists and white supremacist groups, the Justice Department has signaled a new push toward battling domestic terrorism.

Prosecutors have recently described some of those accused of storming the Capitol as participating in acts of domestic terrorism, and House Democrats have introduced a bill that would introduce federal penalties for domestic terrorism.

Domestic terrorism data shows right-wing violence is on the rise in America. Here's how lawmakers and the FBI are responding. (Sarah Hashemi, Monica Rodman, Monica Akhtar/The Washington Post)

Prosecutors say Fox, a member of Three Percenters, an extremist group, had grown increasingly angry over the coronavirus restrictions in Michigan. As retaliation, he allegedly began plotting to kidnap Whitmer, a plan he discussed last June with Croft, a fellow Three Percenter. The two decided they would recruit “like-minded individuals to their cause,” the indictment said.

At a militant-group training camp last August, Fox proposed the kidnapping plot to the other co-defendants, who were members of the anti-government extremist group the “Wolverine Watchmen,” the indictment said. The group soon began surveilling Whitmer’s vacation home and “drew a map” that “noted approximate distances from the home to police first responders,” according to court documents.

The new indictment released this week spells out how the group allegedly planned to attack infrastructure near Whitmer’s house.

On Aug. 30, one of the group members, Ty Garbin, suggested in their encrypted chat that they “take down” a bridge leading to Whitmer’s home to “hinder a law enforcement response,” court documents said. Two weeks later, on Sept. 12, Fox and Croft allegedly went to the bridge to scope out a good spot for a bomb.

Around the same time, Croft and Harris “successfully detonated an improvised explosive device containing shrapnel near human silhouette targets to assess its effectiveness as an anti-personnel weapon,” the indictment said.

On Sept. 13, according to the indictment, Fox ordered $4,000 worth of explosives from a co-conspirator who was actually an undercover FBI agent. On Oct. 7, Fox, Harris and another man, Kaleb Franks, allegedly drove to Ypsilanti, Mich., to purchase the explosives.

But the kidnapping plan fell apart thanks to confidential informants talking to the FBI and sending them recordings of meetings and discussions, prosecutors said. As a result, Fox, Croft, Harris, Franks, Garbin and Brandon Caserta were federally charged with conspiracy to kidnap. Garbin took a plea deal in January and is cooperating with prosecutors.

On Wednesday Fox, Croft and Harris received further charges, including conspiracy to use weapons of mass destruction. Croft and Harris were also charged with possession of an unregistered destructive device, and Harris faces another charge for possession of an unregistered short barrel rifle.

The five defendants face life in prison if convicted of kidnapping conspiracy. The conspiracy to use a weapon of mass destruction also includes a maximum of life in prison. Possession of an unregistered destructive device and short barrel rifle come with sentences up to 10 years each.