UK police still believe London attacker was acting alone

British anti-terrorism police said on Saturday they still believe the man who launched a deadly attack outside parliament this week was acting alone but conceded they may never understand his motive.British-born Islamic convert Khalid Masood, 52, was shot dead after killing four people including a policemen in a rampage on Wednesday when he rammed his car into pedestrians and tried to force his way into the parliament building in central London.Islamic State claimed responsibility for the attack