On Sept. 16, 1931, the Collingwood Massacre brought down several members of the notorious Purple Gang in the Detroit underworld of booze trafficking. The Purple Gang leaders had hired a group of men to work as enforcers in securing liquor shipments from Canada, but the group branched out on their own — creating a turf war. When the men went unarmed to meet with Purple Gang members for what they thought were peace talks, they were gunned down in what became known as the Collingwood Massacre. One man was spared, and he helped prosecutors put three Purple Gang members in prison.
Source: Michigan Every Day
Collingwood Manor Massacre entry from the Encyclopedia of Detroit.
Purple Gang entry from the Encyclopedia of Detroit.
Mark Gribben, The Purple Gang : Collingwood Manor Massacre, CrimeLibrary.