Investigators concluded their son, Sean Petrozzino, 30, was the shooter, who then killed himself after being pulled over in Tennessee.

A new report explains how Petrozzino, a quadruple amputee who lost his hands and legs from a rare form of meningitis, was able to commit the crime.

He was seen using his parents’ ATM card after the killings and quickly became a suspect after physical evidence was connected to the crime.

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In a 12-page report, investigators found despite his physical capabilities, Petrozzino was an avid gun user and altered his weapons to accommodate his disabilities.

A family friend told investigators Petrozzino owned an M-16 assault rifle and tripod which he’s seen him fire, among several other weapons, at a gun range.

The report also found Petrozzino may not have left right after the murders because no shell casings were found at the scene.

Another finding from the report describes how Petrozzino appeared distraught over a break-up with his wife of four years.

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