It was a typical morning in Parliament, as Wednesdays go – the MPs filed into Centre Block for their weekly caucus meetings. Terrorism was front of mind. The Justice Minister stopped and told reporters he was exploring whether to give police new powers to monitor suspects. That's the story I thought I'd file.

Instead, I would soon hear banging and screaming, see smoke and smell gunpowder. I would pull out my cellphone and begin recording, walking into the Hall of Honour connecting the rotunda to the Library of Parliament. Guards were hunting a shooter, rather than chasing one.

Minutes earlier, I'd been sitting in an alcove, just out of sight of the rotunda, headphones in my ears. I was typing. When the banging began, my first thought seemed more plausible than gunfire – I thought a bookshelf had fallen. I took the headphones off as a second bang followed, and many more. Then came the screaming. "Gunfire in pariament [sic]," I tweeted at 9:54 a.m.

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As I peered toward the rotunda, I saw the smoke. Witnesses scrambled past me, fleeing toward the House of Commons side of the building as officers drew their weapons, looking down the Hall of Honour – in many ways a spine of the building, with the House on one side and Senate on the other. It seemed no one knew where the suspect was.

I pulled out my BlackBerry and started recording. I walked toward the rotunda and could hear officers talking. The rotunda has a door out toward the lawn, one the public can use freely as an exit and that MPs, staff and parliamentary journalists can go in and out of with no more than an ID card. There's no metal detector and only a handful of guards. Typically, two right at the door. All signs were the gunman came in that way.

Now, guns drawn, the guards began moving down the hallway. I stopped recording, followed and restarted.

The next video is one you may have seen – it's been widely played in the hours I've since spent locked down in Parliament.

I was following officers going down the hall, which has pillars, alcoves, two hallways at the end on either side before reaching the Library of Parliament – a stunning enclave that's a retreat for many of us on Parliament Hill. A place of calm.

This very hallway had been the scene of a tribute for soldiers who died in Afghanistan. Now guards were moving down it hunting a shooter.

The first door, on the left, is where the Conservatives were having their weekly caucus meeting – the Prime Minister was speaking when the gunfire erupted. To the right was the NDP meeting. More than 300 MPs and senators could, in theory, have been in those rooms.

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Police walked on, and I inched forward. Then another round of shooting broke out.

I ducked for cover to the left of the hallway – that's why the camera shook – while holding the phone out and recording. To be honest, it is a blur. I slid out to a pillar as the shooting continued – most or all of it from guards, aimed toward the library. I heard maybe two dozen shots. Afterward, I turned off the video to tweet photos of what, to me, appeared to be a body. I presume, but don't know, that was the shooter, whom I hadn't seen until then.

An officer pushed me away from the body, and I held my ground, and we argued about my right to be there. I relented and went back to where other journalists – most of them holding TV cameras – had gathered. I texted my fiancée and my parents, letting them know I was safe. We were held in the foyer, where Ottawa Police tactical officers arrived shortly afterward. They aimed their guns at the journalists, screaming to get down on the ground and put our hands up. They quickly moved on. We were moved briefly into the House of Commons lobby – my first time, as journalists aren't usually allowed there – and then down the steps to a ground-level corner of the building, near windows, which we were told to stay away from.

We began to talk – what did we see? What didn't we see? Is everyone safe? Some saw a man with what looked like a rifle. I didn't. One officer told us a guard had been shot in the leg but was okay, and that another was unhurt – shot in the pant leg. Officers periodically came by, sweeping the building with guns or batons – possibly a stun gun – drawn. An MP, who had her infant with her, was swept away to safety. We waited.

After several hours, we were taken to a holding room. Again, it was clear there was no firm plan. I was taken in without being searched or identified. One MP in the room came over and spoke to me, worried that an accomplice or even a shooter could be among the crowd. It seems the crowd was created simply by the room-to-room sweep of the building. We didn't know if we had a shooter in our midst.

As night fell, as I write this, we are still in lockdown. They eventually took MPs and senators out of the holding room first – not the elderly or children, which struck me as just another sign of the confusion. We were told we'd be brought to another building for questioning and to give witness statements.

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The people in this room are shaken, confused, exhausted. Mostly we are just bored and waiting. The reality of being at the heart of the attack is we didn't have all that much information about it – a TV in the corner played updates, and a hush fell over the room when the big news conference began. It was all new to me.

I watched that video again afterward, after it had been on a loop for hours. It seemed new to me, too. The Hall of Honour becoming the site of a crime, the threshold of the library now the scene of an apparent fatality. At least two people are dead in all, one I likely saw and the other a soldier whose photo I saw online. That will take time to sink in. It was chaotic, and heartbreaking. I can't imagine Wednesdays here will ever be quite the same.