British authorities say mental health was a “significant factor” in the London knife attack that killed one person and injured five others Wednesday night, though terrorism has not yet been ruled out. The suspected attacker, identified only as a 19-year-old, has been taken into custody after being tasered by police. He is under police watch at a hospital, according to a statement from Metropolitan police. The stabbing spree at London’s Russell Square at around 10:30 p.m. has prompted extra police patrols in the city starting Thursday. The patrols will include armed officers, and residents have been urged to “remain calm, alert, and vigilant” in light of the attack. The identifies of the victims have not yet been released, but the woman who died was reported to have been in her sixties, and of those injured, two were women and three were men.