Activists are set to form a human chain during a vigil in the western German city of Mannheim on Sunday following a knife attack which left seven people injured. A non-partisan alliance has come forward to organize the human chain, under the motto: “Solidarity against violence, hatred and agitation.” “We want to hold a quiet gathering without slogans and flags,” Green Party city councillor Gerhard Fontagnier told the Mannheimer Morgen newspaper on Saturday. The vigil is supported by a range of political parties represented on the city council, organizers said. It emerged in response to a plann…