One woman is dead, and 5 injured after a man carrying a knife attacked people in London's Russell Square late Wednesday night, Metropolitan Police said.
"A man was arrested at 22:39 hours and a Taser was discharged by one of the arresting officers," police said in a statement.
The man is 19 years old, but his name was not released. At a press conference early Thursday morning, Metropolitan Police Asst. Commissioner Mark Rowley said, "This was a tragic incident resulting in the death of one woman and five others being injured. Early indications suggest that mental health was a factor in this horrific attack.
But Rowley said terrorism isn't being ruled out. "However we are keeping an open mind regarding the motive and terrorism remains one line of inquiry being explored," he said.
The mayor of London, Sadiq Khan, said, "Police have spoken to him and are seeking to establish the full facts including motives for this attack."
Police officers and London Ambulance Service attended to the scene. Additional police units have been deployed to the area to "provide reassurance," police said.
Metropolitan Police's Rowley said, "As a precautionary measure, Londoners will wake up this morning to notice an increased presence on the streets of officers, including armed officers today. We would urge the public to remain calm, alert and vigilant."
Mayor Khan echoed Rowley's comments, saying, "The safety of all Londoners is my number one priority and my heart goes out to the victims of the incident in Russell Square and their loved ones. I have spoken with the Commissioner, and the Assistant Commissioner, who have assured me that our police officers are working extremely hard to investigate exactly what has happened and to keep the rest of us safe. I urge all Londoners to remain calm and vigilant."