LANCASTER, Wis. — A 26-year-old woman was killed and a 17-year-old driver critically injured early Saturday morning in a single-vehicle rollover crash on County Trunk Highway A near Buckwheat Ridge Road in Ellenboro Township.

The Grant County Sheriff’s Office responded to the crash around 2:37 a.m. on May 10, 2026, along with first responders from the Platteville Fire Department and Southwest Health EMS.

According to authorities, Christopher Brandemuehl, 17, of rural Lancaster, was driving a 2007 Ford F350 eastbound on CTH A with passenger Katy Schaefer, 26, of Montfort. The vehicle veered off the south edge of the roadway, crossed the centerline, and entered the north-side ditch. It struck an embankment, rolled multiple times, and came to rest on its driver’s side.

Both occupants were ejected from the vehicle. Schaefer was pronounced dead at the scene. Brandemuehl was airlifted by AirCare3 to UW-Hospital in Madison with critical injuries.

Speed is believed to be a contributing factor in the crash. The highway was closed in both directions for approximately seven hours during the investigation.

The Grant County Sheriff’s Office was assisted at the scene by the Platteville Fire Department, Southwest Health EMS, Lancaster EMS, AirCare3, UW Med Flight, the Wisconsin State Patrol Crash Reconstruction Team, and Bennett’s Towing.

The incident remains under investigation. It marks Grant County’s fourth fatal crash of 2026.