The Okaloosa County Sheriff's Office said results of the autopsy on Demetrius Tillman Nelson are inconclusive.
They said tests did not turn up a cause of death and there were no signs of injuries or medical conditions.
Around midnight Saturday the 44-year-old man, his girlfriend and her three young children pulled into the parking lot of Destin Commons Shopping Complex with car trouble.
Deputies and mall security say Nelson became incoherent and aggressive and grabbed one of the children when they tried to help.
Authorities said Nelson struggled violently even after they used a taser stun gun.
Paramedics examined a cut on nelson's face and he was returned to the patrol car, where authorities said he apparently went into respiratory distress while the ambulance was still on the scene.
The sheriff's office hopes to learn more from toxicology tests that should be back in a few weeks.