COLORADO SPRINGS, Colo. (CBS4) – He threatened to punch a reporter and now U.S. Interior Secretary Ken Salazar says he regrets it.

The subject is controversial. In fact, Salazar says it is the most difficult issue he’s had to deal with, according to the newspaper where the reporter works. It’s not the BP oil spill or fracking, rather the management of wild horses on public land.

READ MORE: Testing For COVID Ramping Up Again In Colorado

It started as a low-key Election Day rally near Colorado Springs. Salazar was getting out the vote for President Obama when a reporter got under his skin and things got weird.

“He was angry saying, ‘If you ever set me up like this again, I’ll punch you out,’ ” said Ginger Kathrens with The Cloud Foundation, a wild horse advocacy group.

Kathrens was videotaping the interview that she says turned ugly when Dave Phillips with the Colorado Springs Gazette asked Salazar about an investigation into Colorado rancher Tom Davis, who is suspected of selling hundreds of wild horses to a Mexican slaughterhouse. The man reportedly has business ties to Salazar and bought the horses from the Interior Department’s Bureau of Land Management.

Salazar was evasive.

“I’m not familiar with exactly what’s going on with Tom Davis,” Salazar said.

READ MORE: Vaccination Rate Keeps Colorado Hospitals Out of Jeopardy

He was also mad. When the interview ended he turned toward Kathrens.

“You know what? You should never do that,” he told her.

“I thought, ‘What does that mean?’ And I turned to ask and he was in Dave’s face,” Kathrens said.

Her video camera was no longer rolling, but the reporter’s audiotape recorder was.

“You should never do that again. This is an Obama event. You know if you do that again I’m going to punch you out,” Salazar is heard saying on the tape.

“I didn’t anticipate that a high-ranking government official would lose it like this,” Kathrens said. “Obviously Dave’s questions hit a raw nerve.”

MORE NEWS: Gov. Jared Polis To Request Federal Disaster Declaration For I-70 Mudslide Damage Through Glenwood Canyon

The Colorado Springs Gazette reported on its website on Wednesday that Salazar called the reporter to apologize and sent him a letter agreeing to an interview.