At the beginning according to the news This is What Happened in London. A man started driving the Vehicle by hitting the pedestrians. Then after the man killed a police officer outside parliament.
This is What Happened in London Attack – London News, Westminster Bridge
Officers on Thursday announced death toll of 4 or 5 members including the police officer. Around 40 people were wounded under this attack. Until now seven people were arrested and officers were searching for the remaining people who were responsible for London Attack.
This incident happened on Westminster bridge on 2.40 PM. After this the parliament of locked and officers began the search of assailants. People wounded on the bridge include school children, police officers and citizens.
After this incident people many people who were moving behind came to rescue the wounded people. Police officers started catching the assailants. According to the report This is What Happened in London Attack.