The Polk County Sheriff’s office has identified a badly injured man found by a snowplow driver Monday morning. 19-year-old Francisco Rodriguez of Mexico City was found by a plow driver who first thought he’d been in a crash during Sunday’s wintry storm. At a Des Moines hospital, doctors determined he’d been beaten, and shot. The sheriff conferred with immigration officials and today announced the investigation’s led to the arrests of three people. A Des Moines man and woman were picked up as material witnesses and 26-year-old Irma Arredondo is charged with attempted murder. A spokesman says the Polk County Sheriff’s department expects to make more arrests but could use help from informants who know the people involved and the events that led up to the man’s discovery on a rural highway in Polk County.