A 74-year-old Wausau man who died after driving his vehicle into a retention pond Sunday in Rib Mountain likely suffered a medical condition before the crash, authorities said Wednesday.

Richard Rademaker was already unconscious when he was pulled from his vehicle, police said.

The single-vehicle crash was reported at about 7:15 p.m. Sunday near Lilac Avenue and Phlox Lane in the town of Rib Mountain.

Two bystanders witnessed the crash and immediately entered the water in an attempt to rescue the driver. Attempts to revive Rademaker by bystanders and SAFER paramedics were not successful and the driver died of his injuries, police said.

Marathon County Medical Examiner Jessica Blahnik declined to specify a cause of death but said a medical condition caused Rademaker to drive off the road.

Full autopsy results are pending.