Members of Parliament dove for cover and barricaded themselves behind tables and chairs as gunfire shattered the peace of their weekly routine caucus meetings Wednesday morning when a gunman stormed Parliament Hill.

In interviews and on social media, MPs painted a picture of the chaos that ensued when .

Video from inside Centre Block shows police officers and security personnel, guns drawn, making their way down the Hall of Honour before gunshots ring out, made even louder by the echo produced by the building鈥檚 high ceilings.

All three parties were holding their caucus meetings when the first gunshots sounded, shortly before 10 a.m.

A handful of MPs began tweeting about hearing the gunshots, with Treasury Board President Tony Clement reporting dozens of shots fired.

While some MPs immediately fled and ended up in lockdown in their offices or other rooms on Parliament Hill, others stayed inside behind locked doors that they barricaded with tables and chairs.

NDP MP Charlie Angus described hearing 鈥渞apid fire鈥� suddenly ring out outside the meeting room door.

鈥淎t that point we assumed that the shooter as on the other side of the door, and it would have been the logical thing that the shooter was trying to come in,鈥� Angus told CTV鈥檚 Canada AM on Friday.

鈥淎nd so we were trying to barricade the doors with tables and chairs and getting people on the ground.鈥�

Sandhu praised a security guard who threw himself in front of the caucus room door and slammed it shut. When the gunfire stopped, a hush fell over the NDP MPs, Sandhu tweeted.

NDP MP Rosane Dore Lefebvre, one of the MPs who fled Centre Block, said she and others were told to run without making noise.

鈥淲e got out and ran,鈥� she told reporters Wednesday morning. 鈥淎nd we could smell the gunpowder.鈥�

Dore Lefebvre鈥檚 toddler daughter was in the Parliament Hill daycare when the shooting began.Her partner, NDP鈥檚 Associate Director of Media George Soule, ran from the party鈥檚 offices six blocks away and into the daycare.

Restricted from leaving the Hill, Soule and his daughter took refuge during the lockdown in Dore Lefebvre鈥檚 office.

Meanwhile, in the Conservative caucus room, their meeting had been underway for about half an hour when the first shots were fired.

Conservative MP Tom Lukiwski said Thursday that about a dozen MPs with backgrounds in law enforcement sprang into action.

While some MPs remained barricaded inside the Conservative caucus meeting room, others that had fled were in lockdown in offices and other undisclosed locations on the Hill.

Meanwhile, the Liberals were also meeting. However, the third party鈥檚 caucus room is not in the same area as the NDP and Conservative rooms. Liberal MPs thought the first gunshots were in fact banging from the construction going on in Centre Block.

鈥淭hat鈥檚 what I thought until the security people came rushing down the halls and shouting, 鈥榦ut, out, out,鈥欌�� Liberal MP John McKay told Canada AM.

The Liberal caucus room has a door to the outside, and so MPs rushed out and ran out to the back of the building.

A construction worker suggested that they hide behind a monument, McKay said, which they did until it was safe to walk around the perimeter of the Hill.

鈥淚t only struck us the magnitude of the event when we got onto Wellington St. and saw the massive security response,鈥� McKay said.

Back in Centre Block, Kevin Vickers, the sergeant-at-arms of the House of Commons, grabbed his gun and went looking for the shooter. He then walked into the Conservative caucus room and told MPs that he 鈥減ut him down,鈥� referring to the gunman.

While Prime Minister Stephen Harper was whisked to an undisclosed location, most MPs remained under lockdown on Parliament Hill until Wednesday evening.