PITTSBURGH — Members of the Pittsburgh Jewish community in the city’s Squirrel Hill neighborhood woke up Monday morning to more vandalism and threats, as if in a recurring nightmare.

Just six years ago, the worst massacre of Jews in the United States happened at the Tree of Life Synagogue, which claimed the lives of 11 worshippers here. Now personal and city property and the Chabad here have been covered in threatening graffiti. Among the messages were ones that said “Jews 4 Palestine” with a red inverted triangle — a mark that symbolizes a target that has been used in videos by Hamas’s military wing to identify Israeli military targets.