Polk County officials say a young woman committed suicide this morning by driving a sport utility vehicle over the earthen dam at Saylorville Lake north of Des Moines. Assistant Chief Dave Shoemaker of the Polk County Sheriff’s Department says it originally seemed to be an accident.A man called around 2:20 a-m and said he witnessed the vehicle going over the dam. The first sheriff’s deputies and state troopers on the scene found the vehicle empty. Shoemaker says officers did hear the victim.They heard splashing in the lake and a female voice calling from the lake, but never saw the woman. Rescue divers were sent to the lake, but Shoemaker says they weren’t able to find the woman in time to save her.Their investigation determined it was a suicide, and they recovered the body of a white female in her mid-20s. The woman’s name is not being released until all her relatives can be notified. Shoemaker says it’s an unusual case, something he’s not seen in 25 years.Shoemaker says the county medical examiner will conduct an autopsy.