In 2014, the Department of Defense sent Blackhawks swooping into Minneapolis and St. Paul by night for urban training exercises. Though they were approved by Minneapolis Mayor Betsy Hodges, the military arrived a day early, taking panicked residents by surprise.

People called 911 and their equally stunned city councilmembers. It was a public relations horror show.

At the time, Hodges requested that the military give residents fair notice before using Minneapolis as a training ground.

Yet on July 19, Longfellow residents were paid a surprise visit by another unexplained Blackhawk, which hovered low in the air for what seemed like hours. Councilman Andrew Johnson noticed the aircraft. He also noticed residents lighting up Facebook, Twitter, and Nextdoor with nervous speculation.

"People were concerned, especially with the timing. It was right after Justine Damond was shot and killed, so they were anxious about law enforcement, to have a military helicopter a few days later hovering over our community so inexplicably," he said. "Nobody knew what was going on. There just wasn't much information about why."

The city hadn't received any notice, Johnson said. So he contacted former Councilman Dennis Schulstad, a retired Air Force officer, who put Johnson in touch with the Minnesota National Guard.

According to Captain Holly Rockow, spokeswoman for the Guard, the Blackhawk was part of a mission that "required the crew to hover the aircraft in different areas over the city to reduce noise and enhance the effectiveness of communication equipment."

That left more questions than answers. Mainly: How an ear-popping helicopter was supposed to reduce noise, and whether the mission was part of some sort of investigation.

General Richard Nash of the National Guard followed up with Johnson, confirming that the helicopter was supporting a Department of Justice operation. The general said he wasn't allowed to share any information, however, and suggested that Johnson make a Freedom of Information Act request.

Johnson has done that, and now awaits the full story. Though there's no telling how long the DOJ will take to respond, he says he's hooked on finding out more.

"A lot of residents were very interested, and from our standpoint, it's important for understanding how the operation came to be and whether there was any consideration toward letting residents know," he says.

"When people are calling 911 and 311 and they're anxious and panicked, we need to have information that can be shared, that can prevent rumors or concerns from escalating."