The death of actress Kristin Cavallari's brother, Michael, who also is the brother-in-law of Chicago Bears quarterback Jay Cutler, was ruled accidental on Tuesday.

A Utah medical examiner determined that the 30-year-old died of hypothermia after walking away from his car in rocky southern Utah terrain in frigid temperatures, according to a press release from the Grand County Sheriff's office.

Grand County Sheriff Steven White said they are waiting on toxicology reports to find out if Cavallari had any drugs in his system. White added that the autopsy report closes the case, but questions may forever linger about what exactly happened.

Also Read: Kristin Cavallari's Brother Michael Found Dead After Being Reported Missing

Cavallari's body was found at the bottom of a steep hillside filled with boulders on Dec. 10, about two weeks after his abandoned car was found with the engine running and the air bag deployed about 200 miles south of Salt Lake City. Investigators believe he was just passing through Utah.

Utah law enforcement was first called in about Cavallari's disappearance on Nov. 27, when it received a report about an abandoned 2014 Honda Civic which appeared to have veered into a ditch 100 feet off Interstate 70.

Associated Press, Star Tribune
In this July 2, 2011, file photo, Chicago Bears quarterback Jay Cutler, left, and his wife Kristin Cavallari watch the Chicago Cubs play the Chicago White Sox in Chicago.

Also Read: Country Singer Craig Strickland Missing After Going Duck Hunting in Massive Storm

Credit card receipts in the vehicle led police to a convenience store in Monticello, Utah, where Cavallari was seen on security footage.

Temperatures in the area were at or below freezing every night in the days after the car was found.