COPENHAGEN (Reuters) -Several people were killed in a shooting at a shopping centre in Copenhagen on Sunday, Danish police said, adding they had arrested a 22-year-old Danish man and could not rule out it was an “act of terrorism”. Copenhagen police said officers had been sent to Field’s mall in the city after reports of a shooting, and had told people inside the centre to stay put and await assistance. There was currently no indication that other shooters were present, police said. The capital’s main hospital, Rigshospitalet, had received a “small group of patients” for treatment, a spokesman…