The department said actions were necessary against those targeting law enforcement.
Streever's email compared Lyons to a Nazi Germany leader and criticized his protection of the officer involved in the Minnesota shooting.
"You are a monstrous human being and will go down in history as America’s Reinhard Heydrich, the butcher," the email read.
The email concluded with personal assertions about Lyons' future peace of mind.
Federal officials also visited poll worker Paigelynne Gonyea at a voting location during New York's primaries the same week to confront her about a social media post concerning the officer who shot Good.
Homeland Security Department spokesperson Lauren Bis stated that sharing an officer's address online is a federal crime.
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The New York attorney general's office is reviewing the interaction between Gonyea and federal agents.
