In Britain, at least four people, including an armed police officer and the attacker, were killed and 20 people injured in a terrorist attack near the Houses of Parliament in London today. <br/><br/>The head of counterterrorism at London's Metropolitan Police, Mark Rowley said the dead policeman was guarding Parliament while the other victims died on Westminster Bridge after the attacker mowed down pedestrians in a car, leaving at least 20 people injured.<br/><br/><br/>At least three other police officers were also injured in the attack. A search is underway to make certain no other attackers are in the area. The incident unfolded this afternoon as a man tried to gain entry into the British Parliament via the main entrance and stabbed a police officer. <br/><br/>The attacker was shot by police. In an incident just minutes earlier, a speeding grey Hyundai i40 mowed down several pedestrians on Westminster Bridge nearby before ramming into the iron railings of the side of the House of Commons building. The driver from this vehicle is believed to be the lone knife-man who then ran out of the vehicle to try and enter the Parliament building. <br/><br/>