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.
Police Chief Brian O'Hara said that the shooting victim's only interaction with law enforcement was traffic tickets.
"We believe he is a lawful gun owner with a permit to carry," the chief said of the man shot by federal agents on Saturday.
Minnesota's gun laws permit open carrying a handgun as long as the gun owner has a valid permit.
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.
