The memo was dated Jan. 28 and signed by by Acting Director Todd Lyons.
A 37-year-old man was shot and killed Saturday morning in Minneapolis -- the second shooting of a U.S. citizen this month by federal agents in the city.
The shooting of Alex Pretti, an ICU nurse, ratcheted up tensions, as protesters clashed in the streets with law enforcement in the aftermath of the shooting.
The incident followed the fatal shooting of Renee Good, a 37-year-old mother, on Jan. 7.
Minneapolis Police Chief Brian O'Hara provided some details about the shooting Saturday and said the victim was a 37-year-old white Minneapolis resident.
"We believe he is an American citizen," he said.
The unidentified man who was reportedly shot by a federal agent Saturday died, DHS said in a statement.
The agency alleged the man "approached US Border Patrol officers with a 9 mm semi-automatic handgun."
"The officers attempted to disarm the suspect but the armed suspect violently resisted. More details on the armed struggle are forthcoming," they added.
DHS said it would release more information.
-ABC News' Luke Barr
Minneapolis state patrol issued a warning to the crowd gathered outside of the shooting, saying the protest was an "unlawful assembly."
They ordered the crowd to disperse.
The FBI agent who began investigating the officer-involved shooting of Renee Good has resigned from the bureau, sources tell ABC News.
After the agent attempted to begin a civil rights investigation, she was told to reclassify it, according to a source.
The New York Times first reported this detail.
-ABC News' Luke Barr
