Updated

A man who froze to death in Wisconsin while sleepwalking outdoors in bare feet sometimes took a sleeping pill, and authorities suspect he had also been drinking before he died.

Investigators found a bottle of Ambien in Timothy Brueggeman's bedroom, but they have not determined whether he took the medication on the night of his death.

Brueggeman, 51, was found outside his rural home Tuesday morning — hours after the temperature plunged to minus 16 Fahrenheit (minus 26 Celsius). He was wearing only underwear and a fleece shirt, and died of hypothermia, authorities said.

Sawyer County Chief Deputy Tim Zeigle said investigators believe Brueggeman may have been drinking before he died. They were awaiting test results to determine whether he had taken Ambien and alcohol together.

Ambien, the most-prescribed sleeping pill in America, has been linked to hundreds of cases of sleepwalking, sleep-driving and even sleep-shoplifting. Sanofi-Aventis, which makes the drug, maintains it is safe when taken correctly and not mixed with alcohol or other drugs.

A longtime friend of Brueggeman, Ed Lesniak, said Brueggeman sometimes drank while taking Ambien.

"He was like a lot of us," Lesniak told the Star Tribune of Minneapolis. "He'd stop off after work or have a couple throughout the evening and then take a pill to go to sleep."

Brueggeman's mother, Geraldine Brueggeman, of Bloomington, Minnesota, said she advised him to quit taking Ambien last summer after he drove his pickup truck without waking up.