A 20-year-old Grayslake man found dead Tuesday after a search by family and friends died of hypothermia, said Lake County Coroner Thomas Rudd.

Volunteers discovered Joey Frase in a field close to Campbell Airport near Grayslake after he was last seen leaving a Round Lake party approximately 1:15 a.m. Sunday.

An autopsy performed Wednesday found some alcohol in his system, according to the coroner, with a blood alcohol level of .09, just above the legal driving limit of .08.

"What we found indicates nothing other than exposure (to cold) and borderline intoxication," Rudd said.

Rudd said it's likely Frase got lost, because Campbell Airport is infrequently used and shuts down its lights when no planes are approaching or departing.

"It had to be extremely dark," Rudd said.

Brett Frase, Joey Frase's father, said his son was an infectiously upbeat person with a love of fishing and the outdoors in general.

"He was a great kid," Brett Frase said. "He was always a happy kid, always smiling."