TULSA, Okla. — The Oklahoma medical examiner has ruled the death of a man killed by a Tulsa County volunteer deputy as a homicide.

An autopsy report released Tuesday shows 44-year-old Eric Harris suffered internal bleeding and collapsed lungs after he was shot April 2 by reserve deputy Robert Bates. Harris' cause of death was a gunshot wound to the back.

The report also found that Harris had methamphetamine in his system when he died.

Bates has pleaded not guilty to a charge of second-degree manslaughter. Bates says he confused his handgun and stun gun after Harris ran from officers during a sting involving gun sales.

A police video shows Harris telling officers he was having trouble breathing after he was shot. A deputy replied with a profanity-laden outburst.