State investigators are calling last week’s death of an Urbandale teenager "suspicious." Eighteen-year-old Jared Parks was found dead on Interstate 35/80 near Des Moines on the night of May 11th.

The Polk County Medical Examiner said Parks died from "multiple blunt-force trauma injuries" after being hit by at least two semis. Authorities are asking for the public’s help as they try to determine how Parks ended up alone on the roadway just before midnight.

Parks was scheduled to graduate from Urbandale High School this week.