Crowds gathered in London’s Trafalgar Square Thursday night to express solidarity with those killed and injured in Wednesday’s Westminster terror attack.

Londoners and tourists stood together in a candlelit vigil, listening to public figures including London Mayor Sadiq Khan and Home Secretary Amber Rudd pay tribute to the victims, especially slain police officer Keith Palmer.

“This a time to express our gratitude to the heroism of our police officers and emergency services who ran towards danger to help, and at the same time they encouraged others to run for safety,” Mr. Khan said.

Meanwhile, Ms. Rudd paid tribute to “courageous and brave” PC Palmer, who was stabbed to death by attacker Khalid Masood.

“I know that all officers of the Met are like that and in my experience, so are all policemen,” she said. “I want us to say thank you to them all for the great sacrifice and risks they take to keep us safe.”