Police in London say a man crashed a car into a group of pedestrians and cyclists before hitting a set of barriers outside of Britain’s Houses of Parliament on Tuesday, causing a number of injuries.

Authorities said officers arrested the male driver of the car on suspicion of terrorist offenses. They said there were no other people in the car, and that they did not find any weapons. They put his age as being in his late 20s.

“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 the suspect is not cooperating with police as they try to establish both the man’s identity and motive.

He 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.

President Donald Trump 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!”

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.