Cummiskey is reputed to have shown Coonan how to dismember and dispose of murder victims by scattering their remains into the waters around the sewage treatment plant, which was operated by the New York City Department of Environmental Protection at Randalls and Wards Islands, notably in the Hudson River.
He had also spent almost a year on the FBI Ten Most Wanted Fugitives list after being a stowaway on an International Longshoremen's Association freighter to Itaguaí, Rio de Janeiro, Brazil to avoid a murder charge.
[citation needed] A longtime gangster of the Manhattan's Westside ghetto known as Hell's Kitchen, Cummiskey served under Mickey Spillane following his release from prison.
He was allegedly involved in the kidnapping of Genovese crime family bookmaker Paul (Eli) Ziccardi as well as later participating in the gang war between Spillane and Jimmy Coonan during the mid-1960s.
While serving time in an upstate New York prison, Cummiskey learned the trade of butchery and became a butcher with the Amalgamated Meat Cutters, allowing him to take advantage of his sentence to perfect a new murder method.
[citation needed] During the early 1970s, Cummiskey took on a young protégé by the name of James "Jimmy C" Coonan, a violent younger generation Irish hoodlum who wanted to take out the old-timer Mickey Spillane.
[citation needed] Cummiskey would further himself from the Spillane-led faction of the Hell's Kitchen Irish Mob known as the Spillane Gang and become more and more a member and follower of the young Jimmy Coonan.
[citation needed] Although reportedly on good relations with both Spillane and Coonan (despite rumors of Cummiskey defecting to the Westies), he was shot at point blank range and killed by Joseph "Mad Dog" Sullivan while drinking at the Sunbrite bar on August 20, 1976.