It was, to be honest, looking like a fairly quiet afternoon when I heard the first bang come from outside.
Looking out of the window of my office in Parliament's Press Gallery, it initially looked like there had been a bus crash.
Then we heard the shouting, and saw people running around on Westminster Bridge.
I noticed a commotion out of the corner of my eye and looked down to see a man rush a security gate about 100 yards away.
He made a bee-line for one of the police officers guarding the area, and the two of them fell to the ground.
Another police officer rushed towards the pair, then I saw the assailant get up and walk towards him with his arm outstretched. He was holding a weapon of some kind, most likely a knife.
Within a couple of seconds I heard the sound of gunfire and that was when it became obvious that a serious incident was underway.
Armed police appeared from everywhere, running around scanning the area to see if any other intruders had entered the parliamentary estate.
An air ambulance arrived at one point, and I saw two people - presumably the attacker and a police officer receiving treatment in New Palace Yard. One received CPR as he was lifted into a waiting ambulance, the other lay motionless as he received treatment.
Myself and the dozens of other journalists who work here were told to stay at our desks as the parliament was in lockdown. Armed police wearing helmets and dark glasses shouted at us to get away from the windows as they tried to make sure the danger had passed.