US Park Police opened an investigation on Thursday into giant markings of the numbers “8647” – which have been associated with opposition to President Donald Trump – on the grass of the National Mall. A spokesperson for the Department of the Interior, which manages the National Mall in downtown Washington, described the incident as “deranged vandalism” and said it “will not be tolerated”. “Any threat against the president is taken very seriously by the department, and our US Park Police will...