Detectives are investigating whether primary school teacher Sabina Nessa was killed by a stranger who is still at large, a senior officer has said. The 28-year-old had been walking to meet a friend at a pub in Kidbrooke, south east London, on a journey that should have taken just five minutes when she was fatally attacked near Cator Park. Speaking at the park where flowers had been laid beside a police cordon, Detective Chief Superintendent Trevor Lawry said he is “keeping a completely open mind” on what the motive of the attacker may have been but is concerned that they are still on the loose. Asked whether the Metropolitan Police are worried that the killer could attack someone else, he said: “We have lines of inquiry that we’re pursuing at the moment. “It’s always a concern that it may happen, but that’s not something that we have any intelligence on …