I wasn't there, so I defer to anyone who was, but ... no steps available? Really? How did the police get onto the aircraft?
To me, something doesn't quite compute. A passenger describes landing at Cologne, waiting for about half an hour while the authorities decide what to do, then police come on board and remove the suspects ('Asian', of course), then also remove the people who'd reported the security risk; then about a quarter hour elapses while this passenger watches from his window as the police 'talk to' the suspects and finally take them away. All this time, the passenger who's speaking seems to have been sitting on the aircraft. Surely by then any competent airport could have produced some sort of steps?
In any case, the emergency slide evacuation (after which 9 people received medical treatment) seems to have taken place only after a long delay. If there was a danger, why not evacuate on landing?
Britons released without charge after Easyjet plane scare - BBC News, 11 June 2017