Complex sentence: Prior to that, he was the 57th U. S. Attorney for the Western District of Pennsylvania; he resigned following the election of President Donald Trump and began his position at Pitt in January 2017.
Split into simpler sentences: Prior to that, he was the 57th U. S. Attorney for the Western District of Pennsylvania. He resigned following the election of President Donald Trump and began his position at Pitt in January 2017.