One officer was standing guard at the entrance to the police station in the north of the city this afternoon.
An ambulance was called there at 11am after an officer was killed in an incident with a firearm.
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On Monday afternoon, numerous Facebook posts claimed a silver Mini had been stolen from the town with a girl in it.
Top temperatures 10 Celsius (50F).
Britain and the European Commission reached agreement on a transition deal which will allow talks on the future trade relationship.