May 12 (UPI) -- A man fatally struck by a Frontier Airlines aircraft on Friday at Denver International Airport died by suicide, a medical examiner said.

Michael Mott, 41, was walking across a runway at 11:19 a.m. Friday as the aircraft was accelerating to take off for a flight to Los Angeles. He died from multiple blunt and sharp force injuries caused by the plane's engine, Dr. Sterling McLaren, the Denver chief medical examiner, said Tuesday at a press conference at the airport, the Denver Post reported.

"As a scientific investigation, we can't really know, really, what someone's intent was," McLaren said. "The best way to determine manner is to evaluate the totality of the investigation - scene findings, circumstances and history. Based on all of those findings together, we determined the manner of death to be suicide."

One of the plane's engines caught fire in the incident, creating a large debris field. Twelve people of the 231 on the plane sustained minor injuries in an evacuation.

Security alarms inside the fence were thought to be caused by a herd of deer near the fence, airport CEO Phil Washington said, according to NBC News. Cameras kept switching between the human intruder and the wildlife, and ditches in the area also may have interfered with the view, Washington said.