Counterterrorism police in Britain are working to figure the motive for a driver crashing into a group of pedestrians and cyclists outside of the Houses of Parliament in London.
The crash Tuesday left three people injured, and police quickly arrested the driver.
Authorities have identified him only as a 29-year-old British national. He is being held on "suspicion of preparation of a terrorist act."
"It certainly appears to be a deliberate act, but what the motivation is we can’t say," London Assistant Commissioner Neil Basu told reporters.
Basu said that based on what investigators know so far, the suspect does not appear to be someone who was previously known to British counterterror or intelligence agencies.
Prime Minister Theresa May wrote in a post on Twitter, "My thoughts are with those injured in the incident in Westminster and my thanks to the emergency services for their immediate and courageous response."
President Donald Trump also reacted to the incident on Twitter, saying "Another terrorist attack in London...These animals are crazy and must be dealt with through toughness and strength!"
Police said a silver Ford Fiesta plowed through a group of pedestrians and cyclists during morning rush hour before crashing into a barrier in front of the Houses of Parliament.
The London Ambulance Service said it treated and transported two people to a hospital, and that neither had injuries that were life-threatening. Basu later said one of the people was being treated for serious injuries, while the second had been released from the hospital. A third person was treated at the crash site.
The area around the crash was closed off, as was a subway station close to the parliament grounds. Parliament is not currently in session.
Last year, a man drove a car into pedestrians on nearby Westminster Bridge, killing four people there before stabbing to death a police officer outside parliament. Police shot that attacker dead.