A man holds a sign that reads “I am Charlie” as he attends a service in Londonderry, for those murdered at Charlie Hebdo magazine in Paris

A man holds a sign that reads “I am Charlie” as he attends a service in Londonderry, for those murdered at Charlie Hebdo magazine in Paris

A man holds a sign that reads “I am Charlie” as he attends a service in Londonderry, for those murdered at Charlie Hebdo magazine in Paris January 8, 2015. France began a day of mourning for the journalists and police officers shot dead on Wednesday morning by black-hooded gunmen who stormed the Paris offices of the weekly satirical magazine Charlie Hebdo, renowned for lampooning radical Islam. REUTERS/Cathal McNaughton (NORTHERN IRELAND – Tags: CRIME LAW POLITICS MEDIA)