A knife-wielding man went on a deadly rampage at the heart of Britain's seat of power Wednesday, first using what NBC News describes as a 4x4 vehicle to mow down pedestrians on London's Westminster Bridge before stabbing an armed police officer to death inside the gates of Parliament. Four people were killed, including the attacker, and about 40 others were injured, the AP reports. Lawmakers, lords, staff, and visitors were locked down as the man was shot by police within the perimeter of Parliament and just yards from entrances to the building itself after he scaled the security wall toward the Parliament's grounds. He died, as did two pedestrians on the bridge, and the police officer. A doctor who treated the wounded said some had "catastrophic" injuries. Three teenage French students were among those injured on the bridge, the Guardian reports.
Police said they were treating the attacks as a terrorist incident and had launched a full counterterrorism investigation. There was no immediate claim of responsibility. "We are satisfied at this stage that it looks like there was only one attacker," said Metropolitan Police counterterrorism chief Mark Rowley. "But it would be foolish to be overconfident early on." The threat level for international terrorism in the UK was already listed at severe, meaning an attack is "highly likely." Wednesday was the anniversary of suicide bombings in the Brussels airport and subway that killed 32 people, and the latest events echoed recent vehicle attacks in Berlin and Nice, France. As lawmakers were voting inside Parliament, many reported hearing the sound of gunshots. Parliament was locked down for two hours, and adjoining Westminster subway station was shuttered. (Read more Britain stories.)