UPDATED: The U.K. Parliament in Central London was on lockdown on Wednesday after a police officer was killed and the alleged assailant shot dead by authorities in a terrorist incident. In a related attack on a nearby bridge, two were killed and at least 20 people were injured.

“It looks like there’s only one attacker,” said Mark Rowley, assistant commissioner of the Metropolitan Police, during a press conference.

A vehicle plowed into a number of people on Westminster Bridge, and then crashed into railings outside Parliament. A man armed with a knife then ran from the car and attempted to force his way past a security check-point at the front of Parliament, and stabbed a police officer, who later died. The attacker was shot dead by police.

The BBC reported that two people died and at least 20 were hurt — including some with “catastrophic” injuries — in the incident on the bridge. One woman was pulled alive from the river and treated for serious injuries.

Police are treating the attacks as a terrorist incident. Commander B.J. Harrington of the Metropolitan Police said: “Although we remain open-minded [as] to the motive, a full counter-terrorism investigation is already underway.”

Shortly after the attacks, David Lidington, the leader of the House of Commons, told lawmakers inside Parliament: “It seems that a police officer has been stabbed, that the alleged assailant was shot by armed police.

“An air ambulance is currently attending the scene to remove the casualties.

“There are also reports of further violent incidents in the vicinity of the Palace of Westminster.”

Daily Mail journalist Quentin Letts, whose office overlooks the scene, told the BBC of the moment police shot the man.

“This man had something in his hand, it looked like a stick of some sort and he was challenged by a couple of policemen in yellow jackets and one of the yellow-jacketed policemen fell down.

“We could see the man in black moving his arm in a way that suggested he was either stabbing or striking the yellow-jacketed policeman, and one of the policemen then ran to get help, which was very quick to come and as this attacker was running towards the entrance used by [Members of Parliament] to get into the House of Commons.

“As he was running — he ran about I’d say 15 yard perhaps — two plain clothes guys with guns shouted at him what sounded like a warning, he ignored it and they shot two or three times and he fell.”

It is exactly a year since the terrorist attacks in Brussels, which left 32 people dead and more than 300 wounded. The attacks were claimed by the so-called Islamic State group.