Lee Impola, 33, the second of two brothers seriously injured in an Independence Township blast July 4, died at Detroit Receiving Hospital Wed., July 25.
Andy Impola, 31, died July 11.
Investigators determined the men were using black powder or flash powder to build illegal M-series explosives in a maintenance building at Lancaster Lakes Apartments, where the younger Impola was employed.
Neighbors raced to help the men, pulling one from the building just before it burst into flames.
The investigation was closed last week after officials ruled the blast was accidental in nature. Police say they are not positive what caused the powder to be ignited; it could have been
anything from open flame to static shock.