Transcript for Capitol Hill police officer breaks his silence after attempted siege
Officer Harry Dunn, one of the capitol police officers who fought off the mob on January 6th. His story was front and center at the impeachment trial. He told his story for the first time publicly to our chief justice kor important Pierre good morning, Pierre. Reporter: George, good morning. Today for the first time we see and hear from a capitol police officer who was a witness to that day of infamy, he's speaking only for himself and not for the department but he has quite a story to tell. He was tested physically and emotionally as he battled that mob in a battle for democracy. So many calls on radio, priority, help, help. Somebody's trapped. We need help. Reporter: When capitol police officer Harry Dunn went to work on the morning of January # 6th it felt like a normal day. What's the first moment that you began to get a sense that something was off kilter here. We were told to get helmets, riot helmets. No sense that all hell could break loose in. Correct. Reporter: The 13-year veteran watched as the crowds of thousands closed in on the east side of the capitol. You see a sea of people, trump flags, confederate flags, don't tread on me flags, then you look down and you see officers fighting with these people, smoke grenades, pepper balls being thrown by everybody. Flash bangs. We fought with these people who were prepared. For a fight. They had on gas masks. They had on body armor. They had on two-way raid owes. They had on tactical gear. Bulletproof vests. They were ready to go. When you see that level of preparedness, did that surprise you? Did it scare you sf. I was scared. I was absolutely scared. I'm on this platform, I'm a big I'm 6'7". I'm this giant person and we had our guns out and I'm thinking, all these people out there zthey're armed, too. I'm like, I'm going to get shot. They're going to take me out. At one point I said, how is this going to end. Reporter: At one point the mob forced its way into the capitol building. I said we got dozens of officers down. Dozens of officers down and you got to nerve to be holding a blue lives matter flag. They instantly said, we're doing this for you. We're doing this for you. And as one of the guys kept walking by the other one pulled out his badge and said, trust me, I understand, we're doing this for you, buddy, he's got a badge. He shows me his badge. What did you think, a fellow officers's -- You got to be kidding me. Reporter: Exhausted officer Dunn tried reasoning with a large group of protesters approaching a hallway he was guarding. I literally told them if they want to get through he you got to go through me and they didn't -- they just started talking to me, they were saying how Joe Biden didn't win the election and nobody voted for him. So I took the bait and, okay, what about me? I voted for Joe Biden, does my vote don't count? He encountered a couple in the crowd who started hurling racial slurs. Hey, this Voted for Joe Biden, guys. Hey, everybody, this Voted for Joe Biden. They said you . The crowd -- Everybody joined in with them. Someone race seeped into that, too. Everybody wants to say that it was about politics and everything. But it was a large number of people in that crowd that were racists. The people who were there tell you why they were there. Stopping the steal. According to us they were doing us a favor. According to those terrorists. You're very precise, you used the word terrorists. Absolutely. To absolutely. They were terrorists. They tried to disrupt this country's democracy. That was their goal. You know what, y'all failed. Reporter: But five people lost their lives that day including capitol police officer Brian sicknick. Officer Dunn had his first chance to reflect on what he witnessed. A cloud of smoke, water bottles, broken flag poles, everything in the rotunda just laying there on the floor. The pinnacle of American democracy. All of this stuff is there. I sat down with a good friend of mine, I said, is this America? What the hell just happened? I told him, I was called [ bleep ] A couple of dozen times today. Protecting this building. Is this America? They beat police officers with blue lives matter flags. They fought us. They had confederate flags in the U.S. Capitol. They stormed the speaker's office. They went through their sensitive documents. They were trying to assassinate the vice president, in the capitol. What's the gamut of emotions? I got angry, I got sad, I got hurt. During this interview, I'm getting angry now but I don't mind talking about it. Reporter: He has nothing but praise for his fellow officers including Eugene Goodman who seen shielding the unguarded senate floor. There were dozens of you Jean goodmans that day, dozens. Eugene got caught on camera. I'm not surprised he did the right thing the brave thing the heroic thing. He deserves everything that he's getting but there were so many Eugene goodmans that weren't caught on camera that day and I'm proud to work with them. Pierre that's so powerful. Officer Dunn reminds us of just how horrifying that day was. How is he doing now. Officer Dunn and his fellow brothers and sisters of the capitol police are still healing on so many levels. As you can see from the interview, it's going to take some time. Boy, it sure is. Pierre, that's really something. You can see more of Pierre's exclusive interview tonight across our ABC news platforms. You could really feel his emotions still.
This transcript has been automatically generated and may not be 100% accurate.