A Milwaukee man believed to be dead gave authorities the surprise of their lives on Saturday when he woke up on the way to a morgue.

Thomas Sancomb suffers from a "severe thyroid issue" and a medical condition that occasionally makes him "feel devoid of vital signs," according to Examiner.com. After the incident, his brother told reporters that the condition makes his body mimic death. Medical examiners confirmed the brother's claim, saying that when Sancomb was found in his bedroom unconscious and presumed "dead," his body was 84 degrees and his neck and jaw muscles were stiff, mimicking rigor mortis.

Sancomb's girlfriend called 911 after not being able to get in touch with him for an extended period of time. When police arrived at Sancomb's home, he was collapsed in his bedroom and "appeared to have died," the incident report stated. A medical examiner was called to move Sancomb to a morgue, but when the examiner arrived Sancomb was moving both his arm and leg. Paramedics were once again summoned to the apartment, where Sancomb was transported to Columbia-St. Mary's Hospital. As of Saturday he was listed in critical condition.

Wisconsin authorities are investigating if "proper procedures" were followed while announcing Sancomb's "death," according to Examiner.com.

"We're doing an internal investigation to make sure that everything we did followed protocol. It's an active investigation, so I can't comment in detail," Assistant Chief Gerard Washington said.

Sancomb's brother said his sibling does not do drugs and only sometimes smokes cigars and consumes alcohol.