SPRINGFIELD, Mo. (AP) — An autopsy says a Springfield man who died after being stunned by police had severe heart failure.

The Springfield News-Leader reports that Phyllis Sanford confirmed this week that the Greene County Medical Examiner’s Office determined that her grandson, Wally McCurdy, died of cardiac arrhythmia brought on by exertion and being high on methamphetamine. His left ventricle also was enlarged and thickened. His death was classified as “accidental.”

Police say the 32-year-old was one of two shoplifting suspects to flee from a Walmart store in April. Officers deployed a stun gun during the chase but McCurdy kept running. When officers caught him, McCurdy wasn’t breathing. He died at a Springfield hospital.

Sanford says she has lots of questions about what happened after her grandson was apprehended. The police investigation remains open.