Hoax threats have spread fear across Germany, with police on high alert after Wednesday’s deadly shooting spree.The scene of the rampage at Winnenden near Stuttgart remains at the centre of the enquiry. But, as mourning there goes on, more than half a dozen copycat threats of violence were made against other schools. As well as in Germany, police in the Netherlands, France and Sweden have also made arrests after Internet messages – most apparently meant as a bad joke – warned of more bloodshed. Authorities now doubt Tim Kretschmer gave notice of his deadly intentions online. Police are continuing to investigate the 17-year-old’s background, looking for clues as to why he killed 15 people before shooting himself dead.