On Wednesday, the North Platte Police Department identified the man as Mitchell William Freeman, whose last known address was in Roseberg, Oregon.
Authorities say family members in Helena, Montana have been contacted and they told an investigator they had been concerned about Freeman's declining health.
Officials have determined the death was a result of natural causes.
Police were called to the vacant lot behind the McDonald's parking lot around 8:30 p.m. Sunday, where Freeman's van with Oregon license plates was located. A passerby had noticed what appeared to be an unconscious man and contacted authorities.