National Geographic photographer Louie Palu spent five years covering the war in Afghanistan. He covered the drug wars in Mexico, including more than 100 assassinations.

He has never seen anything like what he saw Wednesday at the U.S. Capitol — and neither have you.

Palu’s been on a four-month assignment for National Geographic to photograph the 2020 election and its aftermath. He was in the Capitol when a mob supporting President Trump turned violent, storming the building, overwhelming police, and breaking into the Senate and House chambers.

Caught in the middle of the crowd and chaos, putting aside his personal safety, Palu turned on his GoPro. The resulting video thrusts you into a scene that the vast majority of Americans thought would never — and could never — happen in our country.

“I felt like it was such an important moment to make sure there was a record of this,” he told me. “I know this happens in other countries. That’s the extra shock. And the saddest part is that this was done by Americans, to Americans, against their own government. That makes it much harder to swallow than when the British burned the Capitol in 1814.”

These days Palu, 52, says he’s “semi-retired” from covering wars: “I cover politics now.” Luckily, a lot of what he learned from documenting conflict allowed him to stay calm and safe in the middle of utter mayhem.

Palu had gone to the Ellipse, to cover remarks President Trump was making to a rowdy rally of supporters. The crowd was tightly packed, he couldn’t get close enough for a good picture, and hardly anyone was wearing a mask. That was a COVID-19 risk he wasn’t willing to take, so Palu made his way up to Capitol Hill, where the House and Senate were gathered to affirm President-elect Joe Biden’s victory. He thought he’d cover that instead.

He was in a Capitol room reserved for accredited photographers when he heard crowd sounds, so he went outside for a look. He saw that the mob had surged past police lines.

“You get to that decision point,” he told me. “I would be going into a crowd with no police, and very few journalists, but I decided to go down there to document the perspective of the mob. I’m careful with pejorative words like mob,” he added. “But that’s what it was.”

The crowd started moving up the Capitol steps. “Every time the police tried pushing back, there were just too many protesters,” Palu said. A lot of them were “strong, big men,” many of whom were armed with sticks, bats, and flagpoles. A lot of people in the crowd were wearing riot gear, he said: “They had their own helmets, goggles, and shin pads. They came prepared. They were like shock troops.”

He had to decide whether to keep going or back off. The police had lost control. The crowd was a surging, screaming mob. Pepper spray and tear gas were in the air. The COVID-19 risk was off-the-charts. So was the risk to his personal safety.

“The sentiment against journalists is so high,” he said. “What protected me was that they were so focused on the police, and breaking into the Capitol, that they didn’t really see me at all.” He turned on his Go-Pro, knowing the impact of what he was seeing would only partially be captured by pictures. He needed audio.

Palu was back to being a conflict photographer. “When I cover these things, I’m always looking for a pillar or a wall or somewhere I can take cover,” he said. “I look at what people are saying and how they are behaving, so I can gauge the safety of the situation.” What surrounded him, he says now, “felt like a medieval castle siege…I watched the police, who I see every day on the Hill, become totally overrun by a wave of people determined to destroy an imagined enemy.”

“At this point, I thought, ‘I’m in it.’ I just put COVID out of my mind. It was unbelievable. The police here do a phenomenal job, but the number of people and how they were prepared, it was beyond what the police could handle.”

The video tells the rest of the story, showing a mob so out of control that words alone cannot adequately describe it.

“It was the ugliest moment I have ever seen in America,” Palu told me. It also was getting more and more frightening. He worried he might be attacked if people realized he was a journalist; that he might be badly injured, or lose his camera. Finally, there was so much pepper spray and tear gas that he had to pull back.

“It looked to me like they didn’t even know what they were doing anymore except destroying things,” he said of the mob. “They were destroying what they thought they were preserving. That’s the irony — they were destroying the thing they loved.”

At that point he turned around and left the building, taking documentary evidence of a singular event in American history. One thought occupied his mind: “This is going to go out to people, and people can see what it is like.”

The morning after the Capitol siege, Palu texted a colleague. He had barely slept all night, so he’d had time to reflect. “I realize,” he wrote, that “I personally witnessed one of the saddest days I had ever felt in America.”