The Metropolitan Police responded to a security alert on 22 March, following reports that a car had knocked down people on Westminster Bridge. A number of people have been injured, according to reports.The police tweeted that they were called at about 2:40 pm to reports of an incident at Westminster Bridge. Video uploaded to Twitter showed people on the bridge being helped up by other members of the public, as well as the air ambulance landing at Parliament Square. The police said they were treating it as a firearms incident.