(CNN) Federal prosecutors have filed new hate crime charges against the man accused of killing 11 worshippers at a Pittsburgh synagogue last year.

In a superseding indictment returned Tuesday, prosecutors say Robert Bowers used anti-Semitic slurs and criticized a Jewish group on a social media site in the days leading up to the shooting.

Prosecutors also said that Bowers, 46, shot at and shattered a large window in the façade of the synagogue before he entered it.

CNN has reached out to Bowers' lawyer for comment.

Bowers pleaded not guilty in November on the original set of charges. Late last year, famed defense attorney Judy Clarke, who defended Ted Kaczynski and Boston Marathon bomber Dzhokar Tsarnaev, took over Bowers' case.

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