A journalist from German broadcaster Deutsche Welle says Angela Merkel has broken her pelvis in a skiiing accident.
GroKo is short for "grosse Koalition", a grand coaliton of the two large camps from centre-left and centre-right within German politics.
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The memorial service will be attended by Prince Harry and Meghan Markle.
David Browning admits manslaughter by diminished responsibility but denies murder.
Four people have died and the suspect is still at large, police said.