HILLSBORO – Last month, a man found unconscious behind a Hillsboro bar died after what police thought was a drunken fight, but now investigators are at a loss as to what, or who, killed Gerardo Pizano-Arteaga.

Pizano-Arteaga was found barely breathing in a parking lot behind a Hillsboro bar on the morning of September 23rd and initially it appeared that he had been beaten.

Background: Man found unconscious behind bar dies

When an autopsy revealed the extent of his injuries, however, it became clear that a simple fight was out of the question. Medical examiners found his skull had been crushed with more force than any human being could generate.

"Now they're looking at, could it have been a vehicle? Could it have been a car or a truck?” said Hillsboro Police Lt. Mike Rouches.

The fracture to Pizano-Arteaga’s skull told examiners he had been laying on his side at the time of his injury.

Police believe that before his death, Pizano-Arteaga was drunk. But they still have more questions than answers.

Could he have passed out and have been run over?

“I don't know how this could have happened without someone knowing. Even if someone ran over him with a big truck, someone could have felt this,” said Laura Roeter, Pizano-Arteaga's fiancee.

Then again, was Pizano-Arteaga even injured in the parking lot?

The gravel in the lot is large and rough, yet police say the imprint pattern found on the side of the 45-year-old's face was indiscernible.

"We haven't ruled out that there could be another crime scene and that he was left there,” Rouches said.

Without useful surveillance video of the area, investigators are baffled.

A man who was a father and soon-to-be husband is dead and his family and police have no idea why.

Anyone who knows anything about the case is asked to call the Hillsboro Police Department.