The neighbour opened the flat and they found Mackie sitting in a chair in the lounge having died sometime earlier.
Coroner Michael Robb said in his finding police examined the flat and ruled there were no suspicious circumstances.
Mackie was last seen alive on March 13 about 5.30pm when he returned from work in his work truck.
Police found three point bags of synthetic cannabis on a bench top table in the lounge. Two bags were half full and one was empty. A pipe used to smoke synthetic cannabis was found near Mackie.
The finding said a pathologist found Mackie suffered from ischemic heart disease, which is when not enough blood is supplied to the heart. He also suffered from coronary artery atherosclerosis, which is when arteries become blocked.
The toxicology report revealed Mackie had consumed synthetic cannabis in the form of 5F-MDMB-PICA - a potentially deadly drug that had been reported in a number of coronial cases and impaired driving since mid-2017.
Coroner Robb said the synthetic cannabinoid was of high potency that could pose a threat to public health.
However, it couldn't be determined if synthetic cannabis was the cause of death.
"To what extent the consumption of synthetic cannabinoid had on Reece's underlying atherosclerosis and ultimately his death is unable to be quantified."