Bernalillo County sheriff's spokesman Aaron Williamson has said that the motive of the teenage boy who shot dead five people at a home in New Mexico is not yet known, the New York Post reports.
Mr Williamson also said that investigators were trying to determine any connection of the teenager to the victims and if the victims were related.
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The hotel chain said three of its properties - in Maidenhead, Brentford and Tottenham - have been investigated during a detailed assessment
In its first response since the 22-year-old's death, North Korea said Mr Warmbier was treated "according to international standards".
Police would face "real challenges" tackling a repeat of the London riots after years of cuts, one of Britain's most senior officers warns.