October 17, 2:15 p.m., Rescue operation, Stockholm

Emergency services and an ambulance are called to a suspected gas leak in an apartment in Gamla Enskede, and the police also arrive. 
Four adults have fled the home and all four are taken to hospital by ambulance, but only three of them show symptoms such as breathing difficulties and vomiting. 
Emergency services are able to establish relatively soon that no gas leak has occurred, and the police launch a preliminary investigation into causing bodily injury to determine whether a crime has been committed.

But after the people are screened by healthcare staff, food poisoning or an acute outbreak of winter vomiting disease is suspected.