Sadiq Khan said it was 'business as usual' and that Londoners remained defiant after the Westminster terror attack.
British Prime Minister Theresa May said that the "working assumption is that the attacker was inspired by Islamist ideology."
Constable Keith Palmer "left for work [Wednesday] expecting to return home at the end of his shift and had every right to expect that would happen."
Metropolitan Police's Mark Rowley gave more details about investigations into the man who attacked the UK Parliament.
Rescue workers rushed wounded civilians to hospital following an attack outside the UK Parliament.