Karl Zimmermann's journey up to the roof of U.S. Bank Stadium started when he was 14 in the trees near Minnehaha Park, right before he was arrested for the first time.

Zimmermann, who is now 32 and is sometimes called Karl Mayo, a shorter version of his name, was at the park's Camp Coldwater in December 1998 protesting the rerouting of Hwy. 55 over what they said was sacred Native American land. Some 600 law enforcement officers removed activists from the encampment.

As he was led into the police van, his hands bound behind his back, Zimmermann looked past the police tape to see his dad proudly raising a clenched first in solidarity. Dad is Dean Zimmermann, who a couple of years after that incident was elected to the Minneapolis City Council and was once dean of the city's Green Party. The FBI subsequently raided his home and he was convicted of accepting money to support a developer's work in his poor inner city ward.

Karl Zimmermann grew up seeing his family fighting for the rights of American Indians and for environmental protections. When his dad brought him to his first protest over the reroute of Hwy. 55, he felt at home. "They were activists that really had a passion about what they were doing and had a conscience about the world," he said this week. "That's something I wanted to be part of."

Last Sunday he emerged from the protest pack in dramatic fashion during the second quarter of the Vikings' final regular-season game at U.S. Bank Stadium.

As thousands of fans watched, Zimmermann and Sen Holiday, 26, climbed a ladder to a catwalk from which they used carabiners and nylon ropes they'd sneaked into the stadium under their winter coats to rappel down and fly a massive banner urging U.S. Bank to divest from the Dakota Access oil pipeline.

Karl Zimmermann has been an activist from childhood. He was arrested at U.S. Bank Stadium.

They hung some 100 feet high above the seats until the game was over then easily pulled themselves to the awaiting police on the catwalk. Both were arrested and spent the night in jail along with Carolyn Feldman, who supported the action and carried gear. The city attorney's office is investigating and has yet to file formal charges.

Construction of the pipeline has been on hold for several weeks, the result of a yearlong battle between the petroleum industry and a coalition of Indian tribes and environmentalists. Zimmermann says the pipeline dispute is not over though, and the activism is larger than a single pipeline.

A tree sitter in Oregon

To family and friends, Karl Zimmermann is known as Scogin, a family name that is one of his legal middle names along with Mayo. But Karl is his first name and much easier for media to pronounce correctly, he said.

He agreed to talk to bring more attention to the cause, which was also the reason for Sunday's event. He and Holiday were spurred by a call for support from Standing Rock Sioux Reservation. Protesters there wanted help pressuring banks to stop financing the pipeline. U.S. Bank has tens of millions of dollars in credit lines active with the pipeline's parent company, protesters say. The bank has declined to comment.

Zimmermann won't talk specifics about how the protest was planned or executed, but said he and friends wanted to help so they asked, "What is our skill set?" From there, he said they, "threw it together pretty quickly."

Climbing is something Zimmermann and Holiday can do. Zimmermann dropped out of high school when he was 16 and spent the next several years — off and on — in Oregon's Willamette Valley trying to stop old-growth logging. He climbed lots of trees there, both to protest and shield the harvest and to conduct environmental surveys.

Holiday, along with Feldman, was arrested in October 2013 after rappelling down the Washington Avenue Bridge to hang a banner. Police reports don't indicate what the banner said. Like the event at the stadium, the two dangled for a couple hours before ending the protest. She pleaded guilty to a petty misdemeanor for that protest.

By Wednesday, Holiday had already left the Twin Cities and gone to Standing Rock. In August 2012, she was featured on a website for her work with Vegan Outreach, a group fighting animal cruelty. Holiday said at the time that she's from Venice, Fla., and lives in St. Paul. Like Zimmermann, she said her family set her on a path to veganism and "general revolution." She said friends and family are "always there to plot with me to fix this place."

Holiday became a vegan at age 12 and got involved in animal rights activism in high school. She talked about how distributing leaflets helped her get out information and connect with people and urged skeptics to join her. "Come and leaflet with me. It'll be fun," she said.

Zimmermann is similarly encouraging, "Everyone can just go out there and talk to their neighbors and friends and say, 'What are we going to do?' "

Even though he grew up in the heart of Minneapolis, Zimmermann's life now is connected to the earth. He hunts and harvests his own food, including wild rice, beavers, whitefish and lotus. He lives sometimes in a shared house in Minneapolis, but is often in the woods, gathering sustenance both spiritual and edible. "It's an extremely fulfilling way to live and in accordance with my ethics."

When he's around town, Zimmermann earns money helping his 74-year-old dad, who served a 17-month term for the bribes and now works as a handyman.

At his first news conference Tuesday outside the plaza at U.S. Bank Stadium on Tuesday, Zimmermann calmly but consistently rebuffed reporter's repeated questions about his background or how he had pulled off the maneuver at the stadium.

Afterward, his dad, who had witnessed the grilling behind the passel of cameras, wrapped his child in a big hug. "I'm proud of you. Good job," Dean Zimmermann said.

"Thanks," the son responded, "They're persistent, but I guess you know that."

Regardless of what happens at Standing Rock, Karl Zimmermann said his future is clear.

"I expect to be doing this for the foreseeable future. It's who I am," he said, then adding with a friendly laugh, "Keep your eyes open."

Rochelle Olson • 612-673-1747