UPDATE: The police officer who was stabbed by a terrorist who ran over a dozen people has died. He is one of two people confirmed deceased in the attack.
Based off the most reliable sources, it appears that several people were mowed down on the Westminster bridge by a middle-aged person who then crashed into a gate outside of Parliament.
Either the same person or another also stabbed a police officer before being shot. Both the officer and suspect are believed to be wounded but alive.
Today also marks the one year anniversary of the horrific Belgium terror attacks.
It appears the possible explosion reported earlier may have been the vehicle driven by the attacker crashing into the gate or the gunshots by the officers taking down the knifeman.
At least one person and as many as six have been reported shot outside the the Houses of Parliament and Palace of Westminster, according to the BBC and CBS News. One Reuters photographer on scene is reporting that there are over a dozen people injured on the Westminster bridge.
The Prime Minister has been evacuated and the buildings are on lockdown. There are also multiple reports of an explosion, as reported by CNN.
A policeman has been reported stabbed inside Parliament, indicating the possibility of a larger, coordinated attack.
This is a breaking story. We will update as more information becomes available.