It was a Crosby police officer who first heard it: A man, calling out for help from somewhere on Serpent Lake early Monday morning.
Local first responders converged, including the Crow Wing County Sheriff's Office and dive team, Crosby police and fire, and firefighters from Deerwood.
But despite what Crosby PD described as a "gallant" effort, they couldn't get to him in time.
Anthony Bjerkness, 34 years old, was found in the lake's waters, the Crow Wing County Sheriff's Office said. The Ironton man had driven his snowmobile onto Serpent Lake from a nearby road, and got about halfway across.
Then the ice broke.
When first responders arrived, all they found was a snowmobile helmet, along with fresh tracks, InForum reported.
Bjerkness' body was recovered in about 45 feet of water, the sheriff's office said.
"Our thoughts and prayers go out to his family and friends," the office added.
The emergency prompted just the latest warning about thin ice.
Despite the very recent colder weather, many waters still aren't frozen enough to go out on. The DNR says ice should be at least 4 inches thick to walk on, or 5-7 inches to drive a snowmobile on.
One commenter on the Crow Wing County Sheriff's Office Facebook page noted Serpent Lake still has spots of open water.
And even if ice is far thicker than the guidelines posted above, Sheriff Todd Dahl (and the DNR) emphasized that it's never guaranteed to be 100 percent safe.
"Please do not venture out on lakes that you are unfamiliar with and be sure to let someone know where you are going and when you plan to return," Dahl said.